An aircraft constructed with a tractor configuration has the engine mounted with the propeller in front of it so that the aircraft is "pulled" through the air, as opposed to the pusher configuration, in which the propeller is behind the engine and "pushes" the aircraft forward.In the early years of powered aviation both tractor and pusher designs were common. However, by the midpoint of the First World War, interest in pushers declined and the tractor configuration dominated.