Aircraft - a manned or unmanned aerial vehicle heavier than air, kept in the air by the generated supportforce by means of fixed, in given conditions relative to the ship, wings. The sequence needed to maintain speed in horizontal flight is produced by one or more engines. Two types of drives are distinguished: propeller, in which the engine torque is converted into a thrust by means of a propeller ; for this drive, piston or turbine engines are used, a jet engine in which the thrust is produced directly in the engine. Usually, turbojet engines are used, rocket engines are mainly used in experimental constructions or as an auxiliary drive at the start.