Hubbry Logo
Flight planningFlight planningMain
Open search
Flight planning
Community hub
Flight planning
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Flight planning
Flight planning
Flight planning
View on Wikipedia
from Wikipedia

A Tarom Boeing 737-300 and United Airlines Boeing 777-200 taxiing to depart London Heathrow Airport.

Flight planning is the process of producing a flight plan to describe a proposed aircraft flight. It involves two safety-critical aspects: fuel calculation, to ensure that the aircraft can safely reach the destination, and compliance with air traffic control requirements, to minimise the risk of midair collision. In addition, flight planners normally wish to minimise flight cost through the appropriate choice of route, height, and speed, and by loading the minimum necessary fuel on board. Air Traffic Services (ATS) use the completed flight plan for separation of aircraft in air traffic management services, including tracking and finding lost aircraft, during search and rescue (SAR) missions. Flight planning typically includes route selection, fuel calculation, alternate aerodrome planning, weight and balance considerations, and an assessment of meteorological conditions.[1]

Flight planning requires accurate weather forecasts so that fuel consumption calculations can account for the fuel consumption effects of head or tail winds and air temperature. Safety regulations require aircraft to carry fuel beyond the minimum needed to fly from origin to destination, allowing for unforeseen circumstances or for diversion to another airport if the planned destination becomes unavailable. Furthermore, under the supervision of air traffic control, aircraft flying in controlled airspace must follow predetermined routes known as airways (at least where they have been defined), even if such routes are not as economical as a more direct flight. Within these airways, aircraft must maintain flight levels, specified altitudes usually separated vertically by 1,000 or 2,000 ft (300 or 610 m), depending on the route being flown and the direction of travel. When aircraft with only two engines are flying long distances across oceans, deserts, or other areas with no airports, they have to satisfy additional ETOPS safety rules to ensure they can reach an emergency airport if one engine fails.

Producing an accurate optimised flight plan requires millions of calculations, so commercial flight planning systems make extensive use of computers (an approximate unoptimised flight plan can be produced using an E6B and a map in an hour or so, but more allowance must be made for unforeseen circumstances). When computer flight planning replaced manual flight planning for eastbound flights across the North Atlantic, the average fuel consumption was reduced by about 450 kg (1,000 lb) per flight, and the average flight times were reduced by about 5 minutes per flight.[2] Some commercial airlines have their own internal flight planning system, while others employ the services of external planners.

A licensed flight dispatcher or flight operations officer is required by law to carry out flight planning and flight watch tasks in many commercial operating environments (e.g., US FAR §121,[3] Canadian regulations). These regulations vary by country but more and more countries require their airline operators to employ such personnel.

Overview and basic terminology

[edit]

A flight planning system may need to produce more than one flight plan for a single flight:

  • summary plan for air traffic control (in FAA and/or ICAO format)
  • summary plan for direct download into an onboard flight management system
  • detailed plan for use by pilots

The basic purpose of a flight planning system is to calculate how much trip fuel is needed in the air navigation process by an aircraft when flying from an origin airport to a destination airport. Aircraft must also carry some reserve fuel to allow for unforeseen circumstances, such as an inaccurate weather forecast, or air traffic control requiring an aircraft to fly at a lower-than-optimal altitude due to airway congestion, or the addition of last-minute passengers whose weight was not accounted for when the flight plan was prepared. The way in which reserve fuel is determined varies greatly, depending on airline and locality. The most common methods are:

  • US domestic operations conducted under Instrument Flight Rules: enough fuel to fly to the first point of intended landing, then fly to an alternate airport (if weather conditions require an alternate airport), then for 45 minutes thereafter at normal cruising speed
  • percentage of time: typically 10% (i.e., a 10-hour flight needs enough reserve to fly for another hour)
  • percentage of fuel: typically 5% (i.e., a flight requiring 20,000 kg of fuel needs a reserve of 1,000 kg)

Except for some US domestic flights, a flight plan normally has an alternate airport as well as a destination airport. The alternate airport is for use in case the destination airport becomes unusable while the flight is in progress (due to weather conditions, a strike, a crash, terrorist activity, etc.). This means that when the aircraft gets near the destination airport, it must still have enough alternate fuel and alternate reserve available to fly on to the alternate airport. Since the aircraft is not expected at the alternate airport, it must also have enough holding fuel to circle for a while (typically 30 minutes) near the alternate airport while a landing slot is found. United States domestic flights are not required to have sufficient fuel to proceed to an alternate airport when the weather at the destination is forecast to be better than 2,000-foot (610 m) ceilings and 3 statute miles of visibility; however, the 45-minute reserve at normal cruising speed still applies.

It is often considered a good idea to have the alternate some distance away from the destination (e.g., 185 km (100 nmi; 115 mi)) so that bad weather is unlikely to close both the destination and the alternate; distances of up to 960 kilometres (520 nmi; 600 mi) are not unknown. In some cases the destination airport may be so remote (e.g., a Pacific island) that there is no feasible alternate airport; in such a situation an airline may instead include enough fuel to circle for 2 hours near the destination, in the hope that the airport will become available again within that time.

There is often more than one possible route between two airports. Subject to safety requirements, commercial airlines generally wish to minimise costs by appropriate choice of route, speed, and height.

Various names are given to weights associated with an aircraft and/or the total weight of the aircraft at various stages.

  • Payload is the total weight of the passengers, their luggage, and any cargo. A commercial airline makes its money by charging to carry payload.
  • Operating weight empty is the basic weight of the aircraft when ready for operation, including crew but excluding any payload or usable fuel.
  • Zero fuel weight is the sum of operating weight empty and payload—that is, the laden weight of an aircraft, excluding any usable fuel.
  • Ramp weight is the weight of an aircraft at the terminal building when ready for departure. This includes the zero fuel weight and all required fuel.
  • Brake release weight is the weight of an aircraft at the start of a runway, just prior to brake release for takeoff. This is the ramp weight minus any fuel used for taxiing. Major airports may have runways that are about 2 miles (3 km) long, so merely taxiing from the terminal to the end of the runway might consume up to a ton of fuel. After taxiing, the pilot lines up the aircraft with the runway and puts the brakes on. On receiving takeoff clearance, the pilot throttles up the engines and releases the brakes to start accelerating along the runway in preparation for taking off.
  • Takeoff weight is the weight of an aircraft as it takes off partway along a runway. Few flight planning systems calculate the actual takeoff weight; instead, the fuel used for taking off is counted as part of the fuel used for climbing up to the normal cruise height.
  • Landing weight is the weight of an aircraft as it lands at the destination. This is the brake release weight minus the trip fuel burned. It includes the zero fuel weight, unusable fuel, and all alternate, holding, and reserve fuel.

When twin-engine aircraft are flying across oceans, deserts, and the like, the route must be carefully planned so that the aircraft can always reach an airport, even if one engine fails. The applicable rules are known as ETOPS (ExTended range OPerationS). The general reliability of the particular type of aircraft and its engines and the maintenance quality of the airline are taken into account when specifying how long such an aircraft may fly with only one engine operating (typically 1–3 hours).

Flight planning systems must be able to cope with aircraft flying below sea level, which will often result in a negative altitude. For example, Amsterdam Schiphol Airport has an elevation of −3 metres. The surface of the Dead Sea is 417 metres below sea level, so low-level flights in this vicinity can be well below sea level.[4]

Units of measurement

[edit]

Flight plans mix metric and non-metric units of measurement. The particular units used may vary by aircraft, airline, and location across a flight.

Since 1979,[5] the International Civil Aviation Organization (ICAO) has recommended a unification of units of measurement within aviation based on the International System of Units (SI).[6] Since 2010, ICAO recommends using:[7]

However, a termination date for completion of metrication has not been established.[8] While SI units technically are preferred, various non-SI units are still in widespread use within commercial aviation:

Distance units

[edit]

Distances are nearly always measured in nautical miles[citation needed], as calculated at a height of 32,000 feet (9,800 m), compensated for the fact that the earth is an oblate spheroid rather than a perfect sphere. Aviation charts always show distances as rounded to the nearest nautical mile, and these are the distances that are shown on a flight plan. Flight planning systems may need to use the unrounded values in their internal calculations for improved accuracy.

Fuel units

[edit]

Fuel measurement will vary on the gauges fitted to a particular aircraft. The most common[citation needed] unit of fuel measurement is kilograms; other possible measures include pounds, UK gallons, US gallons, and litres. When fuel is measured by weight, the specific gravity of the fuel used is taken into account when checking tank capacity.

There has been at least one occasion on which an aircraft ran out of fuel due to an error in converting between kilograms and pounds. In this particular case the flight crew managed to glide to a nearby runway and land safely (the runway was one of two at a former airport then being used as a dragstrip).

Many airlines request that fuel quantities be rounded to a multiple of 10 or 100 units. This can cause some interesting rounding problems, especially when subtotals are involved. Safety issues must also be considered when deciding whether to round up or down.[citation needed]

Height units

[edit]

The altitude of an aircraft is based on the use of a pressure altimeter (see flight level for more detail). The heights quoted here are thus the nominal heights under standard conditions of temperature and pressure rather than the actual heights. All aircraft operating on flight levels calibrate altimeters to the same standard setting regardless of the actual sea level pressure, so little risk of collision arises.

In most[which?] areas, height is reported as a multiple of 100 feet (30 m), i.e. A025 is nominally 2,500 feet (760 m). When cruising at higher altitudes aircraft adopt flight levels (FLs). Flight levels are altitudes corrected and calibrated against the International Standard Atmosphere (ISA). These are expressed as a three-figure group e.g., FL320 is 32,000 ft (9,800 m) ISA.

In most areas, the vertical separation between aircraft is either 1,000 or 2,000 ft (300 or 610 m).

In Russia, China and some neighbouring areas, altitudes are measured in metres. The vertical separation between aircraft is either 300 metres or 600 metres (about 1.6% less than 1,000 or 2,000 feet).

Until 1999, the vertical separation between aircraft flying at high altitudes on the same airway was 2,000 feet (610 m). Since then there has been a phased introduction around the world of reduced vertical separation minimum (RVSM). This cuts the vertical separation to 1,000 feet (300 m) between flight levels 290 and 410 (the exact limits vary slightly from place to place). Since most jet aircraft operate between these heights, this measure effectively doubles the available airway capacity. To use RVSM, aircraft must have certified altimeters, and autopilots must meet more accurate standards.[citation needed]

Speed units

[edit]

Aircraft cruising at lower altitudes normally use knots as the primary speed unit, while aircraft that are higher (above Mach Crossover Altitude) normally use Mach number as the primary speed unit, though flight plans often include the equivalent speed in knots as well (the conversion includes allowance for temperature and height). In a flight plan, a Mach number of "Point 82" means that the aircraft is travelling at 0.820 (82%) of the speed of sound.

The widespread use of global positioning systems (GPS) allows cockpit navigation systems to provide air speed and ground speed more or less directly.

Another method of obtaining speed and position is the inertial navigation system (INS), which keeps track of a vehicle's acceleration using gyroscopes and linear accelerometers; this information can then be integrated in time to obtain speed and position, as long as the INS was properly calibrated before departure. INS has been present in civil aviation for a few decades and is mostly used in medium to large aircraft as the system is fairly complex.[citation needed]

If neither GPS or INS is used, the following steps are required to obtain speed information:

Mass units

[edit]

The weight of an aircraft is most commonly measured in kilograms, but may sometimes be measured in pounds, especially if the fuel gauges are calibrated in pounds or gallons. Many airlines request that weights be rounded to a multiple of 10 or 100 units. Great care is needed when rounding to ensure that physical constraints are not exceeded.

When chatting informally about a flight plan, approximate weights of fuel and/or aircraft may be referred to in tons. This "ton" is generally either a metric tonne or a UK long ton, which differ by less than 2%, or a short ton, which is about 10% less.

Describing a route

[edit]

A route is a description of the path followed by an aircraft when flying between airports. Most commercial flights will travel from one airport to another, but private aircraft, commercial sightseeing tours, and military aircraft may do a circular or out-and-back trip and land at the same airport from which they took off.

Components

[edit]

Aircraft fly on airways under the direction of air traffic control. An airway has no physical existence, but can be thought of as a motorway in the sky. On an ordinary motorway, cars use different lanes to avoid collisions, while on an airway, aircraft fly at different flight levels to avoid collisions. One can often see planes passing directly above or below one's own. Charts showing airways are published and are usually updated every 4 weeks, coinciding with the AIRAC cycle. AIRAC (Aeronautical Information Regulation and Control) occurs every fourth Thursday, when every country publishes its changes, which are usually to airways.

Each airway starts and finishes at a waypoint, and may contain some intermediate waypoints as well. Waypoints use five letters (e.g., PILOX), and those that double as non-directional beacons use three or two (TNN, WK). Airways may cross or join at a waypoint, so an aircraft can change from one airway to another at such points. A complete route between airports often uses several airways. Where there is no suitable airway between two waypoints, and using airways would result in a somewhat roundabout route, air traffic control may allow a direct waypoint-to-waypoint routing, which does not use an airway (often abbreviated in flight plans as "DCT").

Most waypoints are classified as compulsory reporting points; that is, the pilot (or the onboard flight management system) reports the aircraft's position to air traffic control as the aircraft passes a waypoint. There are two main types of waypoints:

  • A named waypoint appears on aviation charts with a known latitude and longitude. Such waypoints over land often have an associated radio beacon so that pilots can more easily check where they are. Useful named waypoints are always on one or more airways.
  • A geographic waypoint is a temporary position used in a flight plan, usually in an area where there are no named waypoints (e.g., most oceans in the Southern Hemisphere). Air traffic control require that geographic waypoints have latitudes and longitudes that are a whole number of degrees.

Note that airways do not connect directly to airports.

  • After takeoff, an aircraft follows a departure procedure (standard instrument departure, or SID), which defines a pathway from an airport runway to a waypoint on an airway, so that the aircraft can join the airway system in a controlled manner. Most of the climb portion of a flight will take place on the SID.
  • Before landing, an aircraft follows an arrival procedure (standard terminal arrival route, or STAR), which defines a pathway from a waypoint on an airway to an airport runway, so that the aircraft can leave the airway system in a controlled manner. Much of the descent portion of a flight will take place on a STAR.
Airline routes between Los Angeles and Tokyo approximately follow a direct great circle route (top), but use the jet stream (bottom) when heading eastward (Tokyo to Los Angeles)

Special routes known as ocean tracks are used across some oceans, mainly in the Northern Hemisphere, to increase traffic capacity on busy routes. Unlike ordinary airways, which change infrequently, ocean tracks change twice a day, so as to take advantage of favourable winds. Flights going with the jet stream may be an hour shorter than those going against it. Ocean tracks may start and finish about 100 miles offshore at named waypoints, to which a number of airways connect. Tracks across northern oceans are suitable for east–west or west–east flights, which constitute the bulk of the traffic in these areas.

Complete routes

[edit]

There are a number of ways of constructing a route. All scenarios using airways use SIDs and STARs for departure and arrival. Any mention of airways might include a very small number of "direct" segments to allow for situations when there are no convenient airway junctions. In some cases, political considerations may influence the choice of route (e.g., aircraft from one country cannot overfly some other country).

  • Airway(s) from origin to destination. Most flights over land fall into this category.
  • Airway(s) from origin to an ocean edge, then an ocean track, then airway(s) from ocean edge to destination. Most flights over northern oceans fall into this category.
  • Airway(s) from origin to an ocean edge, then a free-flight area across an ocean, then airway(s) from ocean edge to destination. Most flights over southern oceans fall into this category.
  • Free-flight area from origin to destination. This is a relatively uncommon situation for commercial flights.

Even in a free-flight area, air traffic control still requires a position report about once an hour. Flight planning systems organise this by inserting geographic waypoints at suitable intervals. For a jet aircraft, these intervals are 10 degrees of longitude for eastbound or westbound flights and 5 degrees of latitude for northbound or southbound flights. In free-flight areas, commercial aircraft normally follow a least-time-track so as to use as little time and fuel as possible. A great circle route would have the shortest ground distance, but is unlikely to have the shortest air distance, due to the effect of head or tail winds. A flight planning system may have to perform significant analysis to determine a good free-flight route.

Fuel calculation

[edit]

Calculation of fuel requirements (especially trip fuel and reserve fuel) is the most safety-critical aspect of flight planning. This calculation is somewhat complicated:

  • Rate of fuel burn depends on ambient temperature, aircraft speed, and aircraft altitude, none of which are entirely predictable.
  • Rate of fuel burn also depends on airplane weight, which changes as fuel is burned.
  • Some iteration is generally required due to the need to calculate interdependent values. For instance, reserve fuel is often calculated as a percentage of trip fuel, but trip fuel cannot be calculated until the total weight of the aircraft is known, and this includes the weight of the reserve fuel.

Considerations

[edit]

Fuel calculation must take many factors into account.

  • Weather forecasts
The air temperature affects the efficiency/fuel consumption of aircraft engines. The wind may provide a head- or tailwind component, which in turn will increase or decrease the fuel consumption by increasing or decreasing the air distance to be flown.
By agreement with the International Civil Aviation Organization, there are two national weather centres - in the United States, the National Oceanic and Atmospheric Administration, and in the United Kingdom, the Met Office - which provide worldwide weather forecasts for civil aviation in a format known as GRIB weather. These forecasts are generally issued every 6 hours and cover the subsequent 36 hours. Each 6-hour forecast covers the whole world using grid points located at intervals of 75 nautical miles (139 km) or less. At each grid point, the wind speed, wind direction, air temperature is supplied at nine different heights between 4,500 and 55,000 feet (1,400 and 16,800 m).
Aircraft seldom fly exactly through weather gridpoints or at the exact heights at which weather predictions are available, so some form of horizontal and vertical interpolation is generally needed. For 75-nautical-mile (139 km) intervals, linear interpolation is satisfactory. The GRIB format superseded the earlier ADF format in 1998–99. The ADF format used 300-nautical-mile (560 km) intervals; this interval was large enough to miss some storms completely, so calculations using ADF-predicted weather were often not as accurate as those that can be produced using GRIB-predicted weather.
  • Routes and flight levels
The particular route to be flown determines the ground distance to cover, while winds on that route determine the air distance to be flown. Each inter-waypoint portion of an airway may have different rules as to which flight levels may be used. Total aircraft weight at any point determines the highest flight level which can be used. Cruising at a higher flight level generally requires less fuel than at a lower flight level, but extra climb fuel may be needed to get up to the higher flight level (it is this extra climb fuel and the different fuel consumption rate that cause discontinuities).
  • Physical constraints
Almost all the weights mentioned above in "Overview and basic terminology" may be subject to minimum and/or maximum values. Due to stress on the wheels and undercarriage when landing, the maximum safe landing weight may be considerably less than the maximum safe brake-release weight. In such cases, an aircraft that encounters some emergency and has to land immediately after taking off may have to circle for a while to use up fuel, or else jettison some fuel, or else land immediately and risk having the undercarriage collapse.
Further, the fuel tanks have a maximum capacity. On some occasions, commercial flight planning systems find that an impossible flight plan has been requested. The aircraft cannot possibly reach the intended destination, even with no cargo or passengers, since the fuel tanks are not big enough to hold the amount of fuel needed; it would appear that some airlines are over-optimistic at times, perhaps hoping for a (very) strong tailwind.
  • Fuel consumption rate
The rate of fuel consumption for aircraft engines depends on the air temperature, height as measured by air pressure, aircraft weight, aircraft speed relative to the air, and any increased consumption as compared with brand-new engines due to engine age and/or poor maintenance (an airline can estimate this degradation by comparing actual with predicted fuel burn). Note that a large aircraft, such as a jumbo jet, may burn up to 80 tons of fuel on a 10-hour flight, so there is a substantial weight change during the flight.

Calculation

[edit]

The weight of fuel forms a significant part of the total weight of an aircraft, so any fuel calculation must take into account the weight of any fuel not yet burned. Instead of trying to predict the fuel load not yet burned, a flight planning system can handle this situation by working backward along the route, starting at the alternate, going back to the destination, and then going back waypoint by waypoint to the origin.

A more detailed outline of the calculation follows. Several (possibly many) iterations are usually required, either to calculate interdependent values such as reserve fuel and trip fuel, or to cope with situations where some physical constraint has been exceeded. In the latter case it is usually necessary to reduce the payload (less cargo or fewer passengers). Some flight planning systems use elaborate systems of approximate equations to simultaneously estimate all the changes required; this can greatly reduce the number of iterations needed.

If an aircraft lands at the alternate, in the worst case it can be assumed to have no fuel left (in practice there will be enough reserve fuel left to at least taxi off the runway). Hence a flight planning system can calculate alternate holding fuel on the basis that the final aircraft weight is the zero fuel weight. Since the aircraft is circling while holding, there is no need to take wind into account for this or any other holding calculation.
For the flight from destination to alternate, a flight planning system can calculate alternate trip fuel and alternate reserve fuel on the basis that the aircraft weight on reaching the alternate is zero fuel weight plus alternate holding.
A flight planning system can then calculate any destination holding on the basis that the final aircraft weight is zero fuel weight plus alternate holding plus alternate fuel plus alternate reserve.
For the flight from origin to destination, the weight on arrival at the destination can be taken as zero fuel weight plus alternate holding plus alternate fuel plus alternate reserve plus destination holding. A flight planning system can then work back along the route, calculating the trip fuel and reserve fuel one waypoint at a time, with the fuel required for each inter-waypoint segment forming part of the aircraft weight for the next segment to be calculated.
At each stage and/or at the end of the calculation, a flight planning system must carry out checks to ensure that physical constraints (e.g., maximum tank capacity) have not been exceeded. Problems mean that either the aircraft weight must be reduced in some way or the calculation must be abandoned.

An alternative approach to fuel calculation is to calculate alternate and holding fuel as above and obtain some estimate of the total trip fuel requirement, either based on previous experience with that route and aircraft type, or by using some approximate formula; neither method can take much account of weather. Calculation can then proceed forward along the route, waypoint by waypoint. On reaching the destination, the actual trip fuel can be compared with the estimated trip fuel, a better estimate made, and the calculation repeated as required.

Cost reduction

[edit]
Main article: cost reduction

Commercial airlines generally wish to keep the cost of a flight as low as possible. There are three main factors that contribute to the cost:

  • the amount of fuel needed (to complicate matters, fuel may cost different amounts at different airports),
  • actual flying time affects depreciation charges, maintenance schedules, and the like,
  • overflight charges are levied by each country the aircraft flies over (notionally to cover air traffic control costs).

Different airlines have different views as to what constitutes a least-cost flight:

  • least cost based only on time
  • least cost based only on fuel
  • least cost based on a balance between fuel and time
  • least cost based on fuel costs and time costs and overflight charges

Basic improvements

[edit]

For any given route, a flight planning system can reduce cost by finding the most economical speed at any given altitude and by finding the best altitude(s) to use based on the predicted weather. Such local optimisation can be done on a waypoint-by-waypoint basis.

Commercial airlines do not want an aircraft to change altitude too often (among other things, it may make it more difficult for the cabin crew to serve meals), so they often specify some minimum time between optimisation-related flight level changes. To cope with such requirements, a flight planning system must be capable of non-local altitude optimisation by simultaneously taking a number of waypoints into account, along with the fuel costs for any short climbs that may be required.

When there is more than one possible route between the origin and destination airports, the task facing a flight planning system becomes more complicated, since it must now consider many routes in order to find the best available route. Many situations have tens or even hundreds of possible routes, and there are some situations with over 25,000 possible routes (e.g., London to New York with free-flight below the track system). The amount of calculation required to produce an accurate flight plan is so substantial that it is not feasible to examine every possible route in detail. A flight planning system must have some fast way of cutting the number of possibilities down to a manageable number before undertaking a detailed analysis.

Reserve reduction

[edit]

From an accountant's viewpoint, the provision of reserve fuel costs money (the fuel needed to carry the hopefully unused reserve fuel). Techniques known variously as reclear, redispatch, or decision point procedure have been developed, which can greatly reduce the amount of reserve fuel needed while still maintaining all required safety standards. These techniques are based on having some specified intermediate airport to which the flight can divert if necessary;[3] in practice such diversions are rare. The use of such techniques can save several tons of fuel on long flights, or it can increase the payload carried by a similar amount.[9]

A reclear flight plan has two destinations. The final destination airport is where the flight is really going to, while the initial destination airport is where the flight will divert to if more fuel is used than expected during the early part of the flight. The waypoint at which the decision is made as to which destination to go to is called the reclear fix or decision point. On reaching this waypoint, the flight crew make a comparison between actual and predicted fuel burn and check how much reserve fuel is available. If there is sufficient reserve fuel, then the flight can continue to the final destination airport; otherwise the aircraft must divert to the initial destination airport.

The initial destination is positioned so that less reserve fuel is needed for a flight from the origin to the initial destination than for a flight from the origin to the final destination. Under normal circumstances, little if any of the reserve fuel is actually used, so when the aircraft reaches the reclear fix it still has (almost) all the original reserve fuel on board, which is enough to cover the flight from the reclear fix to the final destination.

The idea of reclear flights was first published in Boeing Airliner (1977) by Boeing engineers David Arthur and Gary Rose.[9] The original paper contains a lot of magic numbers relating to the optimum position of the reclear fix and so on. These numbers apply only to the specific type of aircraft considered, for a specific reserve percentage, and take no account of the effect of weather. The fuel savings due to reclear depend on three factors:

  • The maximum achievable saving depends on the position of the reclear fix. This position cannot be determined theoretically since there are no exact equations for trip fuel and reserve fuel. Even if it could be determined exactly, there may not be a waypoint at the right place.
  • One factor identified by Arthur and Rose that helps achieve the maximum possible saving is to have an initial destination positioned so that descent to the initial destination starts immediately after the reclear fix. This is beneficial because it minimises the reserve fuel needed between reclear fix and initial destination, and hence maximises the amount of reserve fuel available at the reclear fix.
  • The other factor which is also helpful is the positioning of the initial alternate airport.

Filing suboptimal plans

[edit]

Despite all the effort taken to optimise flight plans, there are certain circumstances in which it is advantageous to file suboptimal plans. In busy airspace with a number of competing aircraft, the optimum routes and preferred altitudes may be oversubscribed. This problem can be worse in busy periods, such as when everyone wants to arrive at an airport as soon as it opens for the day. If all the aircraft file optimal flight plans then to avoid overloading, air traffic control may refuse permission for some of the flight plans or delay the allocated takeoff slots. To avoid this a suboptimal flight plan can be filed, asking for an inefficiently low altitude or a longer, less congested route.[10]

Once airborne, part of the pilot's job is to fly as efficiently as possible so he/she might then try to convince air traffic control to allow them to fly closer to the optimum route. This might involve requesting a higher flight level than in the plan or asking for a more direct routing. If the controller does not immediately agree, it may be possible to re-request occasionally until they relent. Alternatively, if there has been any bad weather reported in the area, a pilot might request a climb or turn to avoid weather.

Even if the pilot does not manage to revert to the optimal route, the benefits of being allowed to fly may well outweigh the cost of the suboptimal route.

VFR flights

[edit]

Although VFR flights often do not require filing a flight plan,[citation needed] a certain amount of flight planning remains necessary. The captain has to make sure that there will be enough fuel on board for the trip and sufficient reserve fuel for unforeseen circumstances. Weight and centre of gravity must remain within their limits during the whole flight. The captain must prepare an alternate flight plan for when landing at the original destination is not possible.

In Canada, however, the regulations state that "... no pilot-in-command shall operate an aircraft in VFR flight unless a VFR flight plan or a VFR flight itinerary has been filed, except where the flight is conducted within 25 NM of the departure aerodrome."[11]

Additional features

[edit]

Over and above the various cost-reduction measures mentioned above, flight planning systems may offer extra features to help attract and retain customers:

  • Other routes
    While a flight plan is produced for a specific route, flight dispatchers may wish to consider alternative routes. A flight planning system may produce summaries for, say, the next 4 best routes, showing zero fuel weight and total fuel for each possibility.
  • Reclear selection
    There may be several possible reclear fixes and initial destinations, and which one is best depends on the weather and the zero fuel weight. A flight planning system can analyse each possibility and select whichever is best for this particular flight.
  • What-if summaries
    On congested routes, air traffic control may require that an aircraft fly lower or higher than optimum. The total weight of passengers and cargo might not be known at the time the flight plan is prepared. To allow for these situations a flight planning system may produce summaries showing how much fuel would be needed if the aircraft is a little lighter or heavier, or if it is flying higher or lower than planned. These summaries allow flight dispatchers and pilots to check if there is enough reserve fuel to cope with a different scenario.
  • Fuel tank distribution
    Most commercial aircraft have more than one fuel tank, and an aircraft manufacturer may provide rules as to how much fuel to load into each tank so as to avoid affecting the aircraft centre of gravity. The rules depend on how much fuel is to be loaded, and there may be different sets of rules for different total amounts of fuel. A flight planning system may follow these rules and produce a report showing how much fuel is to be loaded into each tank.
  • Tankering fuel
    When aviation fuel prices differ between airports, it can be worth putting in more fuel where it is cheap, even taking into account the cost of extra trip fuel needed to carry the extra weight.[12] A flight planning system can work out how much extra fuel will maximise profit. Note that discontinuities due to changes in flight levels can mean that a difference of as little as 100 kg (one passenger with luggage) in zero fuel weight or tankering fuel can make the difference between profit and loss.[clarification needed]
  • Inflight diversion
    While en route, an aircraft may be diverted to some airport other than the planned alternate. A flight planning system can produce a new flight plan for the new route from the diversion point and transmit it to the aircraft, including a check that there will be enough fuel for the revised flight.
  • Inflight refuelling
    Military aircraft may refuel in midair. Such refuelling is a process rather than instantaneous. Some flight planning systems can allow for the change in fuel and show the effect on each aircraft involved.

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Flight planning

View on Grokipedia
from Grokipedia
Flight planning is the process of producing a that describes a proposed from departure to destination, incorporating route selection, calculations, assessments, and to ensure safe and efficient operations. A flight plan serves as a formal document submitted to air traffic services, detailing critical information such as aircraft identification and type, flight rules (either instrument flight rules (IFR) or ), departure and destination aerodromes, cruising speed and altitude, planned route, estimated off-block time, alternate aerodromes, total fuel endurance, number of persons on board, and emergency equipment. This information supports navigation, coordination, flight information dissemination, alerting services, and preparedness in case of emergencies. Filing is typically completed before departure via electronic systems, written forms, or verbal communication to appropriate air traffic services reporting offices, with mandatory requirements for IFR flights, international operations, and crossings of advisory or national borders. For (VFR), the process often begins with plotting the course on aeronautical charts, such as sectional charts at a scale of 1:500,000, while selecting visual checkpoints like towns or rivers for pilotage navigation. Pilots then measure distances, determine true course, apply wind corrections to compute true heading and groundspeed, account for magnetic variation and deviation to derive compass heading, and estimate en route time and fuel needs based on consumption rates and required reserves. Essential considerations include evaluating weather feasibility, avoiding restricted airspace and terrain hazards, ensuring compliance with regulations like 14 CFR Part 91 for minimum altitudes, and integrating tools such as the E6B flight computer for calculations. Navigation methods encompass for time and distance computations, radio aids like VOR for electronic guidance, and GPS for precise positioning, with pilots advised to cross-verify data and maintain . (IFR) planning follows different procedures, detailed in specialized sections. In contemporary , flight planning increasingly leverages advanced optimization techniques, such as graph-based algorithms like A*, to generate four-dimensional trajectories (, , altitude, time) that minimize burn and emissions while dynamically adjusting for real-time factors including weather forecasts from models like HRRR, airspace constraints, and traffic density. These methods can achieve average savings of 3.4% across diverse scenarios, promoting environmental alongside operational efficiency. Overall, effective flight planning mitigates risks, optimizes resource use, and aligns with international standards set by ICAO Annex 2 for global harmonization.

Introduction

Overview

Flight planning is the pre-flight process by which pilots and flight dispatchers prepare for safe and efficient operations from origin to destination, encompassing route selection, requirements, weather assessment, and adherence to regulatory standards such as those set by the (ICAO). This preparation ensures coordination with air traffic services, mitigates risks from environmental factors, and complies with international rules outlined in ICAO Annex 2, which mandates detailed submissions for (IFR) operations, cross-border flights, and other specified scenarios. Historically, flight planning evolved from rudimentary manual techniques in early to sophisticated digital systems. In the 1920s, pilots relied primarily on —estimating position based on time, speed, and direction—combined with visual pilotage using landmarks, as exemplified by transatlantic attempts like Charles Lindbergh's 1927 flight. By the post-1970s era, the advent of computerized flight management systems and GPS integration revolutionized planning, enabling precise route optimization, real-time updates, and automated fuel calculations that supplanted earlier tools like aids and inertial systems. The importance of thorough flight planning cannot be overstated, as it directly contributes to by preventing incidents like fuel exhaustion, enhances operational efficiency through optimized routes and use, and ensures compliance with global standards. A stark illustration is the 1983 Air Canada Flight 143 incident, known as the "Gimli Glider," where a exhausted its mid-flight due to metric-imperial unit errors in pre-flight calculations and faulty gauges, forcing a glide ; this event underscored the need for rigorous verification protocols to avoid catastrophic failures. Flight planning occurs primarily as pre-flight preparation but may involve in-flight adjustments for deviations due to or traffic, with pilots required to notify accordingly. It differs between commercial and general aviation: commercial operations mandate detailed IFR plans with dispatcher involvement and advanced navigation specs for scheduled passenger or cargo flights, while often uses optional (VFR) plans filed by pilots for non-scheduled, personal, or recreational flights, allowing greater flexibility but still emphasizing safety briefings.

Basic Terminology

In flight planning, a waypoint is defined as a predetermined geographical position specified in terms of coordinates, often used to define (RNAV) routes or flight paths for aircraft employing such systems. These fixed points serve as reference locations for , enabling pilots to follow precise paths between departure and arrival points without relying solely on ground-based aids. An , also known as a destination alternate, is an designated in the where an can land if it becomes impossible or inadvisable to proceed to the intended destination due to , mechanical issues, or other factors. This backup site must meet specific weather minima outlined in regulations, such as those in 14 CFR § 91.169, to ensure safe operations if needed. A NOTAM (Notice to Air Missions) is a notice issued by authorities containing essential information about flight operations that could not be disseminated through standard publications, such as temporary hazards, closures, or restrictions. Pilots must review NOTAMs during preflight planning to avoid potential risks along their route. SID (Standard Instrument Departure) refers to a preplanned (IFR) departure procedure designed to simplify clearance delivery, reduce pilot and controller workload, and facilitate a smooth transition from takeoff to en route climbs, often incorporating noise abatement or traffic flow considerations. Similarly, a STAR (Standard Terminal Arrival Route) is an ATC-coded IFR arrival route established for approaching specific airports, streamlining the transition from en route flight to procedures and enhancing overall system efficiency. Common acronyms in flight planning include ETA (Estimated Time of Arrival), which denotes the projected time an aircraft will reach a specified point, such as the destination or a , aiding in scheduling and . ETE (Estimated Time En Route) represents the anticipated flight duration from departure to a given point or landing, calculated based on planned speed, distance, and winds to inform fuel and timing estimates. A key distinction exists between a direct route and a filed route: a direct route is a straight-line path between two points, typically using RNAV capabilities without intermediate fixes, while the filed route is the complete path specified in the IFR flight plan, which may incorporate airways, waypoints, , , or other segments for compliance with rules and traffic flow. In fuel planning, contingency fuel is additional fuel carried to account for unforeseen en route events like variations, deviations, or air traffic delays, often calculated as 5% of the trip fuel under ICAO guidelines (Annex 6), with FAA practices adopting similar standards in certain operations such as performance-based contingency fuel not less than 5% of en route time. In contrast, reserve fuel is the minimum amount required to complete the flight after arriving at the destination, including time for holding patterns and, if applicable, diversion to an alternate , mandated by regulations such as 14 CFR § 91.151 for VFR or § 91.167 for IFR flights. Cruise altitude describes the constant altitude or maintained during the en route phase of flight, selected based on aircraft performance, , and traffic to optimize efficiency and safety. This differs from a flight level, which is a standardized altitude expressed in hundreds of feet (e.g., FL350 for 35,000 feet) based on a setting of 29.92 inches of mercury, used above the transition altitude to avoid altimeter errors in varying conditions, particularly in high-altitude IFR operations. For instance, below 18,000 feet in the U.S., altitudes are reported relative to local sea-level (QNH), whereas flight levels apply above that threshold for consistency.

Measurement Units

Distance and Speed Units

In flight planning, the (NM) is the primary unit for measuring distances, defined internationally as exactly 1,852 meters to align with Earth's curvature for accurate . This unit equals approximately 1.852 kilometers or 1.15078 statute miles, providing a convenient scale where one NM corresponds to one minute of at the . While kilometers and statute miles are occasionally used in specific regional contexts, the NM predominates globally due to its integration with aviation charts and instruments. The adoption of the NM in aviation reflects a historical transition from statute miles, prevalent in early U.S. operations during the 1920s and 1930s, to a unified international standard established by the (ICAO) in 1947 through resolutions promoting consistency in . This shift, formalized in ICAO Annex 5, allowed non-SI units like the NM for distances exceeding 2-3 nautical miles to maintain operational familiarity while advancing standardization. For speed, the knot (KT) is the standard unit, defined as one NM per hour, equivalent to about 1.852 kilometers per hour or 1.15078 miles per hour. In high-speed commercial jet flight planning, the Mach number supplements knots, representing the ratio of true airspeed to the local speed of sound; Mach 1 equates to approximately 661 KT at sea level under standard atmospheric conditions. Flight planners calculate route distances along great-circle paths, the shortest geodesic routes on Earth's spherical surface, to minimize travel length and optimize efficiency. measures velocity relative to the surrounding air mass, while groundspeed (GS) adjusts TAS for wind effects to determine actual progress over the ground, essential for time and resource estimates.
MeasurementPrimary UnitEquivalent Values
Distance (NM)1 NM = 1,852 m = 1.852 km ≈ 1.151 statute miles
SpeedKnot (KT)1 KT = 1 NM/h ≈ 1.852 km/h ≈ 1.151 mph
These conventions ensure precise coordination in international airspace, with TAS and GS informing broader aspects like requirements.

Fuel and Mass Units

In flight planning, quantity is typically measured in weight-based units such as pounds (lbs) or kilograms (kg), which are preferred for accuracy in calculations due to variations in . Volume-based units like U.S. s or liters are also used, particularly for refueling, but require conversion using specific gravity; for example, Jet A has an approximate of 6.7 lbs per U.S. at standard conditions. Aircraft mass is expressed in kilograms (kg) or pounds (lbs), with key distinctions including zero-fuel weight (ZFW), which encompasses the empty aircraft weight plus payload but excludes usable fuel, and takeoff weight (TOW), which adds the fuel load to the ZFW for determining total operational mass. These units ensure compliance with structural limits, as exceeding maximum ZFW can stress the airframe while TOW affects runway performance and climb rates. In planning applications, fuel density variations with temperature must be accounted for, as lower temperatures increase density (e.g., approximately 0.8 kg/ at 15°C for Jet A), impacting uplift calculations—the process of determining the exact to load for a required . Uplift is computed by adjusting measurements from fuel gauges against real-time density to achieve the planned , preventing overload or shortfall during operations. The (ICAO) standardized metric units in Annex 5 during the 1970s, designating kilograms for mass and liters for fuel volume as primary measures to promote global consistency. However, like pounds and gallons persist in , particularly in the United States, due to historical equipment standards and regulatory practices.

Altitude Units

In aviation flight planning, vertical measurements primarily use feet (ft) as the standard unit, where 1 foot is approximately 0.3048 , though (m) are also employed in some international contexts, particularly in metric-based regions. Heights are distinguished as above ground level (AGL), which measures the vertical distance from the directly below the , or above mean (AMSL), which references a standardized datum accounting for tidal variations. AGL is critical for low-level operations like obstacle avoidance and takeoff/landing clearances, while AMSL provides a consistent global reference for en-route . Altitude systems in flight planning rely on barometric pressure readings from , with flight levels (FL) designated for high-altitude operations above the transition altitude, typically 18,000 feet in many regions, expressed in hundreds of feet under a standard atmosphere (e.g., FL350 denotes 35,000 feet). , obtained by setting the altimeter to the standard pressure of 29.92 inches of mercury (inHg) or 1013.25 hectopascals (hPa), serves as the basis for flight levels and performance calculations, independent of local variations. In contrast, indicated altitude reflects the altimeter's reading with local applied, ensuring accurate clearance below the transition level. Conversions between altitude references involve altimeter settings like QNH, which adjusts the altimeter to read using local sea-level pressure, and QNE, the standard setting of 1013.25 hPa that aligns with for transitioning to flight levels. Pilots switch from QNH to QNE at the transition altitude to maintain separation, with QNH values above standard increasing indicated altitudes and potentially raising the effective transition level. These settings ensure vertical separation and are broadcast via . Regulatory frameworks, such as Reduced Vertical Separation Minimum (RVSM), mandate 1,000-foot separation in feet-based from flight level 290 (FL290) to FL410, implemented globally starting in the late 1990s following ICAO studies initiated in 1982 to enhance capacity while using precise altimetry in feet. This standard applies in approved , requiring altimeters to maintain total vertical error within 200 feet.

Route Description

Route Components

Flight routes in aviation are constructed from standardized components that ensure safe, efficient navigation under (IFR). These include departure procedures, enroute segments, arrival procedures, and approach procedures, each designed to interface with navigation aids and airspace structures. Standard Instrument Departures () form the initial route component, providing a predefined path from the departure end to the enroute structure. are ATC-developed procedures that enhance terminal airspace capacity, minimize noise, and reduce pilot-controller communications by specifying altitudes, headings, and turns, often based on RNAV or VOR/DME . For example, a SID might direct an aircraft to climb on a specific radial from a VOR station to an fix before transitioning to airways. Enroute waypoints constitute the core of mid-flight , serving as reference points along airways or direct paths. These waypoints are typically defined by coordinates, such as N42°34.15' W99°59.38' for the Ainsworth VOR fix, or named intersections like YUBBA INT, which pilots use for course changes, altitude assignments, and position reporting. Waypoints, as geographic fixes in flight , enable precise tracking via ground-based or satellite systems. Standard Terminal Arrival Routes () represent the inbound route component, guiding from enroute into the terminal area for descent and sequencing. STARs are ATC-coded IFR routes that simplify clearance delivery and provide altitude restrictions for efficient , often terminating at an initial approach fix for further vectoring or procedure entry. They may include "descend via" instructions allowing pilots to meet crossing altitudes at designated waypoints. Approach procedures complete the route by directing aircraft to the runway, with types such as Instrument Landing System (ILS) and Required Navigation Performance (RNP) Authorization Required Approach (RNAV). ILS approaches use ground-based localizer and glideslope signals for precision guidance down to decision altitudes as low as 200 feet, ensuring 250 feet of obstacle clearance on final. RNAV approaches, reliant on GNSS, offer flexible paths with lateral navigation (LNAV) or vertical guidance (LPV) minimums, supporting over 7,000 procedures in the National Airspace System as of 2025. Navigation aids underpin these components by providing positional references. (VOR) stations, numbering approximately 850 in the U.S. as of 2025, transmit radials for guidance with ±1° accuracy across frequencies 108.0–117.95 MHz, forming the basis for many waypoints and airways. The FAA's Minimum Operational Network (MON) plan is reducing these further to about 580 by 2030 to prioritize GPS-based . Non-Directional Beacons (NDBs), with fewer than 300 installations remaining as of 2025, operate on 190–1750 kHz to indicate bearings via aircraft direction finders, often paired with (DME) for fixes. Global Navigation Satellite Systems (GNSS), such as GPS with (WAAS), enable (RNAV) by computing positions from at least four satellites, supporting fly-by waypoints where turns begin before the fix and fly-over types requiring exact overflight. Airspace designations influence route component selection to maintain separation and compliance. Class A , from 18,000 feet MSL to FL600, mandates IFR operations and ATC clearance, restricting routes to instrument-equipped and prohibiting (VFR) paths. Class B , surrounding major airports up to 10,000 feet MSL, requires ATC clearance and Mode C transponders, compelling pilots to plan routes with prior approval to avoid delays. Class C , extending to 4,000 feet AGL within 10 nautical miles of airports, demands radio contact and transponders, often necessitating route adjustments for VFR or unequipped flights. Airways like Victor routes (low-altitude VOR-based paths below 18,000 feet MSL) and Jet routes (J routes for high-altitude above FL180) provide structured corridors within Class E , with minimum enroute altitudes ensuring obstacle clearance. For instance, a route might follow V-4 (a Victor airway) between VOR fixes, transitioning to J-501 for oceanic segments.

Assembling Complete Routes

Assembling a complete flight route involves sequencing the primary components—departure procedures, enroute segments, and arrival procedures—to form a cohesive path from origin to destination. This process begins with selecting the departure point, typically the or initial fix at the origin , followed by enroute via airways or direct paths, and concludes with arrival fixes leading to the destination . Pilots or dispatchers ensure the sequence adheres to (ATC) requirements, such as standard instrument departures (SIDs) for initial climbs and standard terminal arrival routes (STARs) for descents. Routes can be constructed using published airways, which are predefined corridors between navigation aids like VHF omnidirectional ranges (VORs), or direct routing, which connects waypoints in a straight line. Published airways, such as Victor (low-altitude VOR-based) or Jet (high-altitude) routes, provide structured paths for instrument flight rules (IFR) operations and are depicted on enroute charts. In contrast, direct routing allows off-airway travel, often shorter but requiring ATC approval to avoid congested or restricted areas. For example, a route from Chicago to New York might sequence a SID from Chicago O'Hare (ORD), follow Jet Route J-90 enroute, then transition to a STAR into John F. Kennedy (JFK). Complete routes are specified in standardized formats to facilitate filing and ATC processing. The International Civil Aviation Organization (ICAO) format, used in Item 15 of the form, employs five-letter waypoint names (e.g., "ROMAN") separated by spaces, with "DCT" indicating direct segments between points. An example route string might read "DCT ROMAN L621 BERUB DCT JFK," where L621 is an airway designator linking waypoints ROMAN and BERUB. Jeppesen notation, commonly used in commercial operations, follows a similar structure but integrates chart-specific abbreviations, such as airway identifiers and direct-to fixes, often prefixed with navigation mode indicators like "GPS" or "DCT" for clarity in flight logs. Waypoints are limited to significant points approximately 200 nautical miles apart outside to maintain precision. Tools for assembling routes include aeronautical charts and digital systems. Sectional charts (scale 1:500,000) and World Aeronautical Charts (WACs, scale 1:1,000,000) enable manual plotting of courses, measurement of distances, and identification of checkpoints like rivers or towns. Flight management systems (FMS) automate this by drawing from databases containing , navaids, waypoints, and procedures; pilots enter routes via a control display unit (CDU), selecting airways or inserting direct-to waypoints to build the legs. For instance, an FMS might sequence a departure SID, append an airway like A3, and add a direct leg to an arrival fix, with the system computing lateral and vertical profiles. Validation ensures the assembled route is legal and safe, checking for penetration of prohibited, restricted, or other special use airspace. Pilots review charts and NOTAMs to confirm compliance with regulations like 14 CFR Part 91, avoiding areas such as military operations zones (MOAs) unless authorized. Additionally, routes consider geodesic paths: great-circle routes follow the Earth's curvature for the shortest distance, ideal for long-haul direct segments, while rhumb lines maintain constant headings along airways for simpler , though slightly longer. FMS tools often default to great-circle calculations for direct routings to optimize efficiency.

Fuel Planning

Fuel Consumption Factors

Fuel consumption in aircraft is influenced by a variety of aerodynamic, operational, and environmental factors that planners must account for to ensure safe and efficient flights. These variables determine the rate at which is burned during different phases of flight, particularly cruise, and can vary significantly based on type and conditions. Accurate assessment of these factors allows pilots and dispatchers to estimate total requirements while minimizing excess load that could further increase consumption. Aerodynamic factors play a central role in fuel use, primarily through drag, which opposes the aircraft's motion and requires to overcome. Drag consists of parasitic components, such as skin and form drag, and induced drag, generated by lift production, particularly during turns or climbs. The (L/D) quantifies aerodynamic efficiency; higher L/D values indicate less needed for level flight, reducing fuel burn—for instance, optimizing wing design can improve L/D by up to 20% in some configurations. Wind conditions further alter effective fuel consumption by affecting (GS): headwinds increase the time and fuel required to cover a by reducing GS, while tailwinds decrease it, potentially saving 5-10% on fuel for long-haul routes. Operational factors, including weight, altitude, and speed, directly impact during planning. Aircraft weight, encompassing passengers, , and itself, increases drag and demands; a 10% weight reduction can lower cruise fuel burn by approximately 7-10% due to reduced induced drag. Optimal cruise altitudes for typically range from 30,000 to 40,000 feet, where thinner air reduces drag and improves , potentially cutting use by 3-5% per 1,000 feet above lower levels, though climb costs must be balanced. Speed choices range and : the best range speed minimizes per distance (often near maximum L/D), while best speed prioritizes loiter time on minimal , differing by about 10-15% in for most jets. Aircraft-specific characteristics, such as engine type and ambient , also govern consumption rates. Engine efficiency varies by design: engines, common in commercial jets, achieve specific fuel consumption (SFC) of around 0.5-0.6 lb/lbf·hr at cruise, outperforming piston engines (SFC ≈0.4-0.5 lb/hp·hr) at high speeds but consuming more at low speeds due to bypass ratios optimizing for subsonic flight. Temperature deviations from the (ISA) affect air and engine performance; temperatures above ISA reduce density, increasing and fuel burn by up to 5% at cruise, while colder conditions can enhance but risk icing. Planners include contingencies for such deviations, like anti-icing systems that add 1-3% to total for potential encounters. Representative examples illustrate these effects in practice. A in cruise burns approximately 4,500–5,500 pounds (2,040–2,500 kg) of per hour at typical weights and altitudes, with variations based on load and winds; for instance, a 50-knot headwind could increase total required by about 15% over a 1,000-nautical-mile leg. These rates, often expressed in pounds or kilograms per hour, underscore the need to integrate all factors for precise .

Fuel Calculation Procedures

Fuel calculation in flight planning involves determining the total fuel required for a safe and efficient flight by accounting for various operational phases and regulatory minima. The core approach breaks down the total fuel into discrete components: trip fuel, which covers the actual enroute consumption; contingency fuel, typically 3-5% of trip fuel to account for unforeseen delays; alternate fuel for diversion to an alternative airport; and final reserve fuel, mandated by regulations to handle emergencies. This structured method ensures compliance with safety standards while minimizing excess weight. The basic formula for total fuel is expressed as: Total Fuel = Trip Fuel + Contingency Fuel + Alternate Fuel + Final Reserve Fuel Trip fuel is calculated as Trip Fuel = (Distance / ) × , where distance is the great-circle or planned route distance in nautical miles, (GS) is the aircraft's expected speed over the ground in knots, and is the average consumption in pounds or kilograms per hour. For more precise estimates, planners integrate across flight phases—climb, cruise, descent, and —using aircraft-specific data. (FF) during powered phases is often derived from FF = SFC × , where SFC is the specific fuel consumption (typically 0.5-0.6 lb/lbf-hr for modern engines) and is the engine output in pounds-force. These values are obtained from manufacturer charts or flight systems (FMS), which automate phase-specific integrations. Block fuel represents the total quantity loaded at departure, encompassing taxi fuel (for engine start and runway movement, often 5-10 minutes at idle), trip fuel, and all reserves. Procedures begin with estimating taxi fuel from -specific data, followed by enroute calculations adjusted for and effects on burn rates—hotter conditions increase and thus consumption. Regulatory requirements vary by operation type; for example, under FAA 14 CFR §91.167 for IFR flights, enough fuel to complete the flight to the first of intended (and to the alternate if required), plus 45 minutes at normal cruising speed. ICAO 6 specifies a final reserve of 30 minutes of holding fuel at 1,500 feet (450 m) above the destination or alternate (if required), assuming all engines operating, with similar minima for extended-range operations. Software tools like or approximate these via databases of aircraft performance profiles, reducing manual chart interpolation errors.

Optimization Strategies

Efficiency Improvements

Flight planners enhance efficiency by optimizing routes to leverage favorable wind patterns, such as s, which provide tailwinds that reduce fuel consumption and flight time. For instance, on routes like Haneda to , algorithms incorporating data can shift paths northward to capture winds up to 100 m/s, resulting in fuel burn reductions compared to direct coastal routes adhering to safety constraints. This wind-optimized routing balances economy and risk, using models like Dijkstra’s algorithm with aircraft performance data from sources such as ’s Base of Aircraft Data (BADA). Step climbs further improve long-haul by allowing to ascend incrementally to higher altitudes as burn lightens the , accessing thinner air for better specific range. In multi-altitude trajectories, this technique enables wind-optimal paths across varying flight levels, saving approximately 3.2% and 1.2% travel time on flights like those with a 777-200, equating to about 2 tonnes of on international sectors. Optimization involves two-stage processes: determining step climb timings based on burn rates and then computing horizontal trajectories using like Pontryagin’s Minimum for minimum-time paths in winds. Such adjustments are particularly effective on routes exceeding 1,000 nautical miles, where multiple climbs (e.g., three steps) outperform constant-altitude cruising. Speed management in cruise plays a critical role, with planners selecting economic speeds that balance use and schedule constraints, often around 0.80 Mach for , close to the maximum range speed where drag is minimized relative to . Unlike , where best range occurs at lower speeds due to power-based propulsion, jets achieve optimal range near their long-range cruise , as improves with velocity in this regime. Flight management systems use cost indices to fine-tune this, prioritizing savings over time for economy-focused operations. Load planning minimizes weight impacts on efficiency by optimizing cargo and passenger distribution to maintain an aft center of gravity (CG), which reduces induced drag and improves specific range. For example, shifting CG aft from 20% to 37% mean aerodynamic chord on an A340-600 saves up to 1,550 kg of fuel on a 6,000 nm sector, as aft positions lower trim drag without compromising stability. Planners use weight and balance software to ensure CG stays within limits, avoiding forward CG penalties that increase fuel burn by up to 1.8% on aircraft like the A310. This approach also integrates with approach procedures, such as continuous descent approaches (CDA), where idle-thrust descents from cruise minimize level-offs and speed adjustments, yielding fuel savings of 30-70 kg on single-aisle jets like the A320 or up to 500 kg on larger aircraft when airspace permits. Airlines like Southwest have implemented single-engine taxiing since the early 2000s as a practical efficiency measure, shutting down one engine during ground operations to save approximately 2 gallons of fuel per minute, contributing to broader ground fuel reductions of 5-10%. This initiative, part of investments exceeding $658 million in fuel-saving programs since 2002, aligns with operational goals to cut 100 million gallons of jet fuel from 2025 to 2030, enhancing overall efficiency without specialized technology.

Reserve Fuel Adjustments

Reserve fuel in flight planning encompasses specific components designed to address unforeseen events while preserving safety margins. Contingency fuel, typically 3–5% of the planned trip fuel, compensates for enroute deviations such as adverse winds, routing changes, or air traffic delays; under ICAO standards, this is the greater of 5% of trip fuel or 5 minutes of holding fuel at 1,500 feet above destination elevation. Alternate fuel covers the requirements from a at the destination to a complete at the designated alternate , including climb, cruise, descent, and approach phases. Final reserve fuel ensures the aircraft can hold for 30–45 minutes at holding speed and 1,500 feet above the alternate (or destination if no alternate is required), with the exact duration varying by regulation. Regulatory minima for these reserves differ by operation type to reflect operational risks and oversight levels. For FAA Part 121 commercial operations, the final reserve is 30 minutes of holding fuel, integrated into broader fuel supply rules that also mandate contingency and alternate provisions. In contrast, Part 91 IFR flights require sufficient fuel to reach the alternate plus an additional 45 minutes at normal cruising speed. These standards ensure a buffer against exhaustion, with operators required to plan accordingly unless exceptions apply, such as waiving the alternate when destination forecasts indicate ceilings of at least 2,000 feet and of 3 miles for one hour before and after estimated arrival time. Adjustments to reserve fuel aim to minimize uplift without compromising safety, often through targeted waivers and analytical methods. Under EASA regulations, operators may reduce contingency fuel to 3% of trip fuel if an enroute alternate is selected and weather conditions permit, provided a consumption monitoring is in place to validate planning accuracy. For known favorable weather at the destination, alternate fuel can be waived entirely, eliminating the need for diversion planning fuel. analysis further enables lower contingency levels by leveraging historical flight and statistical models to predict consumption variability, allowing tailored uplifts that align with operational probabilities rather than fixed percentages. Risk assessment underpins these adjustments, using probability models to quantify diversion likelihood and ensure reserves cover low-probability events. Operators must demonstrate through safety performance indicators that reductions do not elevate fuel exhaustion risks, often via simulator validations or historical incident analyses. Balancing regulatory minima like FAA and EASA requirements against empirical data from flight operations supports this approach. A key example of reserve adjustments occurs in long-range ETOPS flights for twin-engine aircraft, where fuel planning accounts for the maximum diversion time to the nearest suitable from the most critical enroute point. This may reduce overall reserves compared to non-ETOPS routes by optimizing alternate selections within the certified diversion limit (e.g., 180 minutes), provided engine reliability and adequacy are verified.

Special Flight Types

VFR Planning

Visual Flight Rules (VFR) planning emphasizes navigation by visual reference to the ground and surrounding terrain, suitable for operations in good weather conditions where pilots maintain direct sight of the ground or landmarks. Basic VFR weather minima require, in Class G airspace below 1,200 feet above the surface during daytime, a minimum visibility of 1 statute mile and remaining clear of clouds for fixed-wing aircraft other than helicopters. Route planning under VFR relies on sectional aeronautical charts, which depict terrain, landmarks, airports, and airspace at a scale of 1:500,000 to facilitate visual navigation for slow- to medium-speed aircraft. Pilots select prominent visual references such as rivers, highways, towers, or towns as checkpoints to track progress along the route. VFR flight plans are not required by regulation for domestic operations but are strongly recommended, particularly for cross-country flights, to enable activation if needed. Fuel planning for VFR flights in airplanes must ensure sufficient supply to reach the first point of intended landing, considering and forecast , plus an additional 30 minutes of reserve during daytime operations or 45 minutes at night. Key navigation tools for VFR include pilotage, which involves correlating the aircraft's position with visible landmarks on charts, and , a computational method using known , time, and heading to estimate position while correcting for wind effects. avoidance is critical, with regulations mandating a minimum altitude of 1,000 feet above the highest within a horizontal radius of 2,000 feet over congested areas such as cities or open-air assemblies. In contrast to more rigid instrument procedures, VFR planning supports shorter, direct routes without reliance on standard instrument departures () or arrivals (), commonly applied in cross-country flights in like the Cessna 172. These routes often incorporate basic components such as visual waypoints for simplicity and flexibility in .

IFR Planning

Instrument Flight Rules () planning is essential for operations in or , where pilots rely on instruments and (ATC) guidance rather than visual references. Unlike () planning, which emphasizes direct visual navigation, IFR requires a mandatory filed submitted to FAA facilities at least 30 minutes prior to departure to ensure timely clearance issuance. This plan details the proposed route, altitudes, and other critical elements to integrate safely with the . IFR routes are structured along federal airways, jet routes, or (RNAV) paths, with altitudes assigned as flight levels above 18,000 feet (MSL) to standardize pressure settings and prevent mid-air collisions. primarily depends on RNAV systems, which enable precise waypoint-to-waypoint travel using GPS or inertial reference systems (IRS), supplemented by ground-based aids like VORs. Pilots must include clearance limits in their planning, anticipating ATC instructions that may amend the route, including expected further clearance (EFC) times for time-based restrictions. Alternate airports are required unless the destination forecast indicates ceilings of at least 2,000 feet above the airport elevation and of 3 miles from one hour before to one hour after the . For the alternate itself, standard minimums apply: 600 feet and 2 miles for airports with precision approaches, or 800 feet and 2 miles for non-precision approaches. Fuel planning under IFR, per 14 CFR § 91.167, mandates sufficient reserves to reach the first destination, proceed to the alternate (if filed), and then hold for an additional 45 minutes at normal cruising speed. Plans often incorporate holding patterns, allocating extra fuel for potential ATC-directed holds, typically 30-45 minutes depending on aircraft type and route complexity. In commercial jet operations, IFR plans frequently designate multiple alternates based on en route weather and ETOPS requirements for twin-engine aircraft, ensuring redundancy over oceanic or remote areas. Post-9/11 security measures have enhanced protocols for flights near sensitive like the Washington, D.C. Special Flight Rules Area (SFRA), requiring specific pilot training and equipment compliance, while standard IFR flight plans detail and operational information for and safety.

Regulatory and Practical Aspects

Filing Flight Plans

Flight plans are submitted to air traffic control authorities to ensure safe and efficient airspace management, with the International Civil Aviation Organization (ICAO) format serving as the standard for most filings in the United States. This format, documented on FAA Form 7233-4, includes key elements such as the departure aerodrome (Item 13, e.g., KJFK), destination aerodrome (Item 16, e.g., KLAX), route description (Item 15, specifying waypoints, airways, or direct segments like "DCT VOR1 VOR2"), and fuel endurance (Item 19, expressed in hours and minutes, e.g., 0500 for five hours). The format is mandatory for IFR flights, all flights departing U.S. domestic airspace into international airspace, Defense Visual Flight Rules (DVFR) operations, and VFR flights in designated areas such as Special Flight Rules Area (SFRA) or Air Defense Identification Zone (ADIZ); domestic VFR flight plans are optional. Electronic submission is facilitated through approved systems such as Flight Service, accessible via 1800wxbrief.com, or via the Automated Flight Service Station (AFSS), now managed by Flight Service. Pilots can file online through portals like 1800wxbrief.com, by telephone to Flight Service at 1-800-WX-BRIEF, or using aviation apps that interface with these systems, ensuring the plan is transmitted to the appropriate Air Route Traffic Control Center (ARTCC). For domestic flights, plans should be filed at least 30 minutes prior to the estimated time of departure (ETD) to allow for clearance processing and avoid delays. International flights follow similar timing under FAA guidelines, though some foreign service providers may require submissions up to three hours in advance for coordination. To secure prompt approvals, pilots often file conservative routes—such as longer paths along preferred airways or avoiding high-density —that align with management preferences, reducing the risk of rerouting delays. In-flight amendments are possible by contacting via radio, where pilots request changes to route, altitude, or destination; ATC issues a revised clearance if traffic permits, with the amendment transmitted as an "AM" message in the system. If a flight becomes overdue—defined as 30 minutes past the estimated time of arrival () without communication for VFR or DVFR plans—Flight Service initiates a communications search, escalating to an Alert Notice (ALNOT) and search-and-rescue (SAR) activation approximately one hour later if the aircraft remains unlocated. Variations in filing include DVFR plans for visual flights within Air Defense Identification Zones (ADIZ), which require an ICAO-format submission with "D" entered in Item 8 (type of flight) and are processed similarly to VFR but with additional defense coordination. Military filings differ from civil ones primarily in procedural oversight: U.S. Department of Defense (DOD) aircraft may use DD Form 1801 for DVFR or stereo routes, often clearing through base operations (BASOPS) for overseas flights, while civil plans adhere strictly to FAA channels without such military-specific routing. Both, however, integrate into the shared for SAR purposes.

Integration of Weather and Airspace

In flight planning, meteorological data integration begins with key sources such as METARs, which provide current airport observations including visibility, wind, and temperature, and TAFs, which offer terminal aerodrome forecasts for up to 30 hours ahead, enabling pilots to anticipate conditions at departure, destination, and alternates. SIGMETs further alert to significant hazards like severe or icing over a broad area, prompting route deviations to avoid unsafe altitudes or paths. For instance, forecasts of moderate to severe may necessitate rerouting around convective activity, while icing SIGMETs require selecting altitudes above or below freezing levels to prevent accumulation. Airspace considerations are equally critical, involving adherence to (FIR) and Upper Flight Information Region (UIR) boundaries, which delineate jurisdictional areas for air traffic services and require flight plans to specify entry and exit points for international coordination. Temporary Flight Restrictions (TFRs) must be avoided, as they prohibit or limit operations in areas due to events like VIP movements or natural disasters, often checked via NOTAMs during preflight. In congested airspace, planners prioritize preferred routes—predefined high- or low-altitude paths between major airports—to enhance traffic flow and reduce delays, as outlined in FAA publications. Planning adjustments incorporate these elements by selecting alternates based on TAF forecasts; for IFR flights, an alternate is required if the destination is forecasted below 2,000 feet above or under 3 statute miles from one hour before to one hour after estimated arrival time, per 14 CFR § 91.169. Wind aloft forecasts, derived from upper-air data, inform fuel tweaks by accounting for headwinds that increase consumption or tailwinds that extend range, often adjusting planned burn by 5-10% in variable jet streams. Tools facilitating this integration include Graphical Forecasts for Aviation (GFA), introduced by the in 2018 as an evolution of text-based area forecasts dating back to the 1990s, providing layered maps of clouds, icing, turbulence, and winds for route visualization. Real-time updates via , a datalink system operational since the 1970s and integrated with flight management since the late 1980s, deliver enroute METARs, SIGMETs, and wind corrections to refine plans dynamically without voice radio.

Modern Tools and Enhancements

Software and Automation

Flight planning has increasingly relied on specialized software to streamline complex calculations, ensure compliance with regulations, and optimize operational efficiency. These digital tools integrate vast databases of aeronautical information, weather data, and performance models to generate comprehensive flight plans, reducing the manual workload on pilots and dispatchers. Core applications include mobile-based platforms like , which provides electronic charts, navigation logs, and weight-and-balance computations for users, allowing real-time updates during pre-flight preparation. Similarly, FliteDeck offers iPad-optimized features for commercial pilots, including dynamic charting and procedure visualization tailored to airline operations. For larger-scale airline operations, systems like Lido and Flight Management Systems (FMS) integrate route optimization with fuel management, pulling from global navigation databases to compute trajectories that account for aircraft performance and airspace constraints. These tools automate the generation of routes using standardized databases such as , which encodes navigation waypoints, procedures, and performance data in a machine-readable format to ensure across systems. Automation extends to real-time wind optimization, where software algorithms adjust flight paths mid-planning to minimize fuel burn by leveraging forecasted wind aloft data from sources like NOAA. The evolution of flight planning software traces back to the , when mainframe-based systems like the early versions of Sabre's flight planning modules began automating basic route and fuel computations for major carriers. By the , personal computers enabled more accessible tools, paving the way for today's cloud-integrated platforms. In the , AI-driven enhancements have emerged, such as for delay forecasting, which use to analyze historical flight data and suggest contingency routes, as implemented in systems like those from . These software solutions deliver significant benefits, including error reduction and time savings; minimizing human oversight in and weight calculations. Overall, such enhances safety and cost-effectiveness, with studies indicating up to 5% savings through precise route adjustments.

Emerging Technologies

and are revolutionizing flight planning through advanced predictive modeling and optimization. In , AI models like DeepMind's GenCast, introduced in 2024, enable probabilistic predictions up to 15 days ahead, surpassing traditional methods in accuracy for ensemble forecasting, which aids in preempting disruptions for safer route adjustments. For (UAM), AI-driven dynamic routing algorithms optimize trajectories in dense low-altitude environments, incorporating on , , and constraints to minimize and enhance safety; for instance, hybrid AI systems for 4D trajectory management support high-density operations by predicting conflicts and suggesting reroutes. These applications extend to broader route optimization, where analyzes historical data to forecast and refine fuel-efficient paths, potentially reducing emissions by up to 10% in simulated scenarios. Blockchain technology enhances the security of flight plan sharing, while space-based Automatic Dependent Surveillance-Broadcast (ADS-B) extends surveillance coverage. platforms facilitate tamper-proof and decentralized sharing of s among facilities, ensuring and reducing risks of unauthorized alterations in collaborative environments. Complementing this, space-based ADS-B, operational since via the Aireon system hosted on NEXT satellites, provides global tracking over oceanic routes previously reliant on procedural separation, enabling reduced spacing from 50 to 30 nautical miles and more direct paths that save airlines approximately $300 in fuel per flight. This integration of with ADS-B-like surveillance promises verifiable, real-time plan dissemination, particularly for unmanned and international operations. Sustainability-focused technologies are integrating into flight planning to address environmental impacts of emerging types. For electric and hybrid in eVTOLs, specialized battery range calculators model energy consumption under variable conditions like wind and , optimizing mission profiles to extend operational range beyond 100 nautical miles while accounting for degradation over cycles. Carbon offset integration embeds emission calculations directly into planning software, allowing pilots and operators to select routes with built-in offsets via schemes like ICAO's CORSIA, where investments in verified reduction projects compensate for CO2 outputs, promoting net-zero strategies without altering core flight paths. Despite these advances, challenges persist in cybersecurity and regulatory frameworks. Automated flight planning systems face vulnerabilities to cyber threats, such as spoofing of AI inputs or ledger manipulations, necessitating robust and to protect against disruptions that could compromise integrity. Regulatory lag exacerbates adoption hurdles for UAM, as seen in the FAA's 2025 proposed rules for beyond-visual-line-of-sight operations, which aim to standardize low-altitude integrations but highlight delays in certifying AI-enhanced systems amid evolving safety standards.

References

  1. https://www.faa.gov/sites/faa.gov/files/18_phak_ch16.pdf
  2. https://skybrary.aero/articles/flight-plan
  3. https://repository.gatech.edu/server/api/core/bitstreams/8b15c12a-8e1e-4736-b72c-42dd5fe1272e/content
  4. https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/air_traffic_services/flight_plan_filing
  5. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap5_section_1.html
  6. https://planeandpilotmag.com/the-evolution-of-navigation/
  7. https://www.aopa.org/news-and-media/all-news/2000/july/pilot/the-gimli-glider
  8. https://www.somasoftware.com/post/what-is-a-flight-plan
  9. https://www.faa.gov/air_traffic/publications/atpubs/pham_html/chap20_section_5.html
  10. https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-91/subpart-B/subject-group-ECFRef6e8c57f580cfd/section-91.169
  11. https://www.faa.gov/about/initiatives/notam/what_is_a_notam
  12. https://www.faa.gov/air_traffic/publications/atpubs/pcg_html/glossary-s.html
  13. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap5_section_4.html
  14. https://www.faa.gov/air_traffic/publications/atpubs/pcg_html/glossary-e.html
  15. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap5_section_3.html
  16. https://www.faa.gov/documentlibrary/media/notice/n_8900.383.pdf
  17. https://www.icao.int/publications/Documents/Annex6_part1_cons_en.pdf
  18. https://skybrary.aero/articles/altitude-flight-level-and-height
  19. https://simpleflying.com/aviation-nautical-miles/
  20. https://simpleflying.com/nautical-miles/
  21. https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part1_gen_section_2.1.html
  22. https://applications.icao.int/postalhistory/annex_5_units_of_measurement_to_be_used_in_air_and_ground_operations.htm
  23. https://simpleflying.com/aviation-knot-speed-guide/
  24. https://aerospaceweb.org/question/atmosphere/q0102c.shtml
  25. https://www.oag.com/blog/great-circle-routes-flight-paths
  26. https://www.boldmethod.com/blog/lists/2024/10/the-four-types-of-airspeed-and-how-each-one-works/
  27. https://www.faa.gov/air_traffic/publications/atpubs/fss/AppendixA.htm
  28. https://www.faa.gov/sites/faa.gov/files/2023-09/Weight_Balance_Handbook.pdf
  29. https://www.engineeringtoolbox.com/jet-fuel-temperature-density-petroleum-volume-correction-ASTM-D1250-gravity-d_1944.html
  30. https://www.navblue.aero/aircraft-weight/
  31. https://simpleflying.com/how-temperature-affects-the-fuel-uplift-for-airliners/
  32. https://skybrary.aero/articles/altimeter-pressure-settings
  33. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap7_section_2.html
  34. https://www.faa.gov/air_traffic/separation_standards/rvsm
  35. https://skybrary.aero/articles/reduced-vertical-separation-minima-rvsm
  36. https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/instrument_procedures_handbook/FAA-H-8083-16B.pdf
  37. https://www.faa.gov/air_traffic/flight_info/aeronav/procedures/ifp_inventory_summary/
  38. https://www.faa.gov/about/officeorg/headquartersoffices/ato/navigation-programs/vor-mon-outreach-presentations/2025-oshkosh-vor-mon-nextgen-dme-programs.pdf
  39. https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_4.1.html
  40. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap1_section_2.html
  41. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap3_section_3.html
  42. https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_3.1.html
  43. https://www.faa.gov/documentLibrary/media/Order/FAA_Order_8260.19H_CHG-01_Only_vs02.pdf
  44. https://skybrary.aero/articles/flight-plan-completion
  45. https://recursosdeaviacion.com/wp-content/uploads/2020/05/introduction-to-jeppesen-navigation-charts.pdf
  46. http://helitavia.com/avionics/TheAvionicsHandbook_Cap_15.pdf
  47. https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_5.1.html
  48. https://www.icao.int/sites/default/files/sp-files/environmental-protection/Documents/Publications/6401_en.pdf
  49. https://www.faa.gov/sites/faa.gov/files/07_phak_ch5_0.pdf
  50. https://ntrs.nasa.gov/api/citations/20160006027/downloads/20160006027.pdf
  51. https://arc.aiaa.org/doi/pdf/10.2514/3.58535
  52. https://www.faa.gov/sites/faa.gov/files/12_phak_ch10.pdf
  53. https://www.aopa.org/news-and-media/all-news/2012/march/pilot/isa-and-cruise-planning
  54. https://www.faa.gov/sites/faa.gov/files/03_amtp_ch1.pdf
  55. https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/sfc.html
  56. https://www.universalweather.com/blog/international-standard-atmosphere-how-it-affects-flight-understanding-the-basics/
  57. https://simpleflying.com/boeing-737-max-airbus-a320neo-mpg/
  58. https://www.faa.gov/documentlibrary/media/advisory_circular/120-42b.pdf
  59. https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-91/subpart-B/subject-group-ECFRef6e8c57f580cfd/section-91.167
  60. https://www.law.cornell.edu/cfr/text/14/121.639
  61. https://ffac.ch/wp-content/uploads/2020/09/ICAO-Annex-6-Operation-of-Aircraft-Part-I-International-commercial-air-transport.pdf
  62. https://www.icas.org/icas_archive/ICAS2022/data/papers/ICAS2022_0652_paper.pdf
  63. https://aviationsystems.arc.nasa.gov/publications/2014/JAIS_Ng_2014_01_Preprint.pdf
  64. https://www.boldmethod.com/learn-to-fly/aerodynamics/best-range-speed-prop-vs-jet/
  65. https://ansperformance.eu/library/airbus-fuel-economy.pdf
  66. https://blog.openairlines.com/what-you-need-to-know-about-continuous-descent-approach
  67. https://www.dlr.de/en/images_archive/2010/1/continuous-descent-approach-cda-landing-profiles_13782
  68. https://mobile.southwest.com/swa-resources/pdfs/one-report/2024-One-Report-5-29-final.pdf
  69. https://skybrary.aero/articles/fuel-flight-planning-definitions
  70. https://aerospace.honeywell.com/content/dam/aerobt/en/documents/landing-pages/brochures/N61-126-000-001_Honeywell_Forge_Managing_Fuel-wp.pdf
  71. https://code7700.com/fuel_minimums.htm
  72. https://www.ecfr.gov/current/title-14/chapter-I/subchapter-G/part-91/subpart-B/section-91.167
  73. https://aerospace.honeywell.com/us/en/about-us/news/2022/06/navigating-understanding-easa-latest-fuel-energy-requirements
  74. https://www.ecfr.gov/current/title-14/chapter-I/subchapter-G/part-121/subpart-U/section-121.619
  75. https://aerospace.honeywell.com/content/dam/aero/en-us/documents/learn/about-us/blogs/gated-content/White-Paper-Managing-Contingency-Fuel-Uplight-with-Advanced.pdf
  76. https://www.sciencedirect.com/science/article/pii/S0969699716304513
  77. https://tc.canada.ca/en/aviation/publications/safety-criteria-approval-extended-range-twin-engine-operations-etops-tp-6327
  78. https://www.federalregister.gov/documents/2007/01/16/07-39/extended-operations-etops-of-multi-engine-airplanes
  79. https://www.faa.gov/air_traffic/flight_info/aeronav/productcatalog/vfrcharts/sectional/
  80. https://www.faa.gov/documentLibrary/media/Form/FAA_7233-1_5-11-17.pdf
  81. https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-91/subpart-B/subject-group-ECFR4d5279ba676bedc/section-91.151
  82. https://www.law.cornell.edu/cfr/text/14/91.119
  83. https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_3.5.html
  84. https://www.law.cornell.edu/cfr/text/14/91.169
  85. https://www.faa.gov/air_traffic/flight_info/aeronav/acf/media/Presentations/21-01-361-Alternate-Mins-Explanatory-Text.pdf
  86. https://www.law.cornell.edu/cfr/text/14/91.167
  87. https://www.faa.gov/sites/faa.gov/files/2022-11/INFO_08004.pdf
  88. https://www.ecfr.gov/current/title-14/chapter-I/subchapter-G/part-135/subpart-D/section-135.223
  89. https://www.faa.gov/media/76196
  90. https://www.faa.gov/air_traffic/publications/atpubs/fs_html/appendix_a.html
  91. https://www.faa.gov/air_traffic/publications/atpubs/fs_html/chap6_section_2.html
  92. https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_1.10.html
  93. https://nbaa.org/aircraft-operations/airspace/tfm/tools-used-for-traffic-flow-management/routes-reroutes-severe-weather-avoidance-plan-swap/
  94. https://www.faa.gov/air_traffic/publications/atpubs/fs_html/chap3_section_4.html
  95. https://www.faa.gov/air_traffic/publications/atpubs/atc_html/chap2_section_2.html
  96. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap7_section_1.html
  97. https://pilotinstitute.com/airmets-vs-sigmets/
  98. https://www.weather.gov/media/publications/front/06nov_Front.pdf
  99. https://skybrary.aero/articles/flight-information-region-fir
  100. https://www.faa.gov/air_traffic/publications/atpubs/foa_html/chap18_section_17.html
  101. https://www.cfinotebook.net/notebook/weather-and-atmosphere/winds-and-temperatures-aloft.php
  102. https://www.weather.gov/media/boi/iwaws/IWAWS_GFAUserGuide.pdf
  103. https://www.faa.gov/sites/faa.gov/files/15_phak_ch13.pdf
  104. https://www.openairlines.com/
  105. https://www.honeywell.com/us/en/press/2019/03/honeywell-software-helps-j-air-lower-fuel-costs-and-improve-fleet-performance
  106. https://deepmind.google/blog/gencast-predicts-weather-and-the-risks-of-extreme-conditions-with-sota-accuracy/
  107. https://www.sciencedirect.com/science/article/pii/S1270963824005534
  108. https://www.researchgate.net/publication/377567173_Role_of_AI_in_weather_prediction_flight_planning_route_optimization_and_scheduling
  109. https://arxiv.org/pdf/2110.08883
  110. https://aireon.com/space-based-ads-b-no-longer-concept-operational-reality/
  111. https://ntrs.nasa.gov/api/citations/20190000022/downloads/20190000022.pdf
  112. https://www.researchgate.net/publication/379025670_Maximum_total_range_of_eVTOL_under_consideration_of_realistic_operational_scenarios
  113. https://www.iata.org/en/programs/sustainability/carbon-offset/
  114. https://www.researchgate.net/publication/364211469_Securing_ADS-B_data_transmissions_using_blockchain_a_comprehensive_survey_and_analysis
  115. https://www.federalregister.gov/documents/2025/08/07/2025-14992/normalizing-unmanned-aircraft-systems-beyond-visual-line-of-sight-operations
Add your contribution
Related Hubs
User Avatar
No comments yet.