Jet engine in which a turbine-driven compressor draws in and compresses air, forcing it into a combustion chamber into which fuel is injected. Ignition causes the gases to expand and to rush first through the turbine and then through a nozzle at the rear. Forward thrust is generated as a reaction to the rearward momentum of the exhaust gases. The turbofan or fanjet, a modification of the turbojet, came into common use in the 1960s. In the turbofan, some of the incoming air is bypassed around the combustion chamber and is accelerated to the rear by a turbine-operated fan. It moves a much greater mass of air than the simple turbojet, providing advantages in power and economy. See alsoramjet.