Getting aloft requires more than lift; it also takes thrust. Thrust provides the forward motion needed to sustain lift and counteract drag. It is also used to accelerate, gain altitude, and sometimes to maneuver.

Propulsion is the act of moving or pushing an object forward. The word is derived from two Latin words: pro, meaning before or forward, and pellere, meaning to drive. A propulsion system is an engine that produces thrust to push an object, such as an airplane or rocket, forward.

Douglas DC-3

The most successful airliner in history, the Douglas DC-3 dominated both commercial and military air transportation from its introduction in 1935 until after World War II. It was the first airplane that could make money by carrying only passengers. This DC-3 flew nearly 57,000 hours for Eastern Air Lines from 1937 to 1952.  Learn more about the history of air transportation

Credit: National Air and Space Museum, Smithsonian Institution