An airline seat is a seat on an airliner in which passengers are accommodated for the duration of the journey. Such seats are usually arranged in rows running across the airplane's fuselage. A diagram of such seats in an aircraft is called an aircraft seat map. Within the industry, this map is known as a LOPA (Layout-Passenger Accommodation).

Seats are attached to rails underneath the floor which run along the aircraft fuselage. If the airline wants to reconfigure the seating, this is a minor operation. For passenger safety, all airline seats are equipped with seatbelts.

Seats are frequently equipped with further amenities. Airline seats may be equipped with a reclining mechanism for increased passenger comfort, either reclining mechanically (usually in economy class and short-haul first and business class) or electrically (usually in long-haul first class and business class). Most aircraft also feature trays for eating and reading, either in the seatback which folds down to form a small table in most economy class seats, or inside the armrest which folds out in most first class, business class, bulkhead, and exit row seats. Most airline seats also feature a pocket which may contain an in-flight magazine and safety instructions.

On small and short-haul aircraft, or on low-cost carriers, some of these amenities may not be installed. For instance, on several aircraft, Ryanair has installed non-reclining seats without seat pockets with the safety manuals stitched to the seat back instead. Even on airliners with reclining seats, some seats may have a restricted recline or no recline. Typically, this will be the rear row of the cabin where a rear bulkhead blocks the recline, or seats immediately in front of the emergency exit where a reclined seat might restrict access to the emergency exit, creating a potential safety hazard. Independent seat review sites such as SeatGuru often warn passengers against these seats. During take-off and landing, the crew asks passengers to put their seats in an "upright" (unreclined) position and to lift and stow their tray tables.

Seats may be equipped with power ports (either EmPower, AC, DC, or USB power-only sockets) for small electrical appliances and ports for headphones for the audio entertainment. Most full-service airlines also include personal video screens as part of the in-flight entertainment system on long-haul aircraft - but some aircraft use a bring-your-own-device system where passengers use their own devices. The screens are often touchscreens or can be controlled by remote handsets. In economy and premium economy, the screen is normally in a seatback, but in a front row seat or premium cabin, they may need to be pulled out from a special compartment after takeoff, and then returned there for landing.

Most long-haul aircraft (and short-haul aircraft on some airlines) feature seats with adjustable headrests in all classes, allowing the passenger to adjust the headrest for comfort.

Electrically adjustable lumbar support is found on most long-haul first-class and business-class seats. Rarely, economy class may also include a mechanically adjustable lumbar support on some long-haul aircraft. However, with the trend towards slimline seats in economy class, this amenity has mostly vanished from most new economy class seat installations.

Some business class seats, such as the Recaro CL 4420, have a built-in massaging feature.