Aircraft engine

An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many small UAVs have used electric motors.

As of 2025, four European and American manufacturers dominate the global market for aircraft engines:

The market for aircraft engines, especially jet engines, has very high barriers to entry. Aircraft engines use highly advanced technology and materials, take around eight years and billions of dollars or euros to develop, and must pass exacting safety certifications by aviation safety authorities.

Consequently, entering the engine market is extremely capital- and time-intensive, which helps protect existing manufacturers from competition. The last successful entry in the global market for jet engines was General Electric in the 1970s. But these barriers to entry make the market very lucrative for existing manufacturers. As of 2025, the leading jet engine manufacturers reported shareholder returns from between 100 and 1,000 percent over the last five years, compared to small or negative returns for their principal clients, Airbus and Boeing.

The engines themselves are typically sold at a loss, but manufacturers derive their profits from the sale of maintenance services and spare parts over the roughly thirty-year lifespan of an engine, following the razor and blades business model. This creates a perverse incentive for manufacturers to slow the production or delay the delivery of new engines, because they profit most from the use of old engines, which need more service and spare parts than new ones. This contributed to the unavailability of new engines creating a bottleneck for Airbus and Boeing's efforts to ramp up aircraft production in the post-COVID resurgence of aviation after 2023.

For other configurations of aviation inline engine, such as X-engines, U-engines, H-engines, etc., see inline engine (aeronautics).

A radial engine has the cylinders placed in a circle around the crankshaft. The engine is air-cooled, which can be a problem since they may overheat. Compared to liquid-cooled engines, radial engines have the advantage of being more rugged and capable of absorbing damage.

Rotating radial engines have the cylinders in a circle around the crankcase, as in a radial engine, (see above), but the crankshaft is fixed to the airframe and the propeller is fixed to the engine case, so that the crankcase and cylinders rotate. The advantage of this arrangement is that a satisfactory flow of cooling air is maintained even at low airspeeds, retaining the weight advantage and simplicity of a conventional air-cooled engine without one of their major drawbacks. The first practical rotary engine was the Gnome Omega designed by the Seguin brothers and first flown in 1909. Its relative reliability and good power to weight ratio changed aviation dramatically.