A fixed-wing aircraft generates forward thrust when a spinning propeller moves air , or gases are ejected from a jet engine ( or rocket engine ) , opposite the direction of flight . A fixed-wing aircraft generates forward thrust when air is pushed in the direction opposite to flight . This can be done in several ways including by the spinning blades of a propeller , or a rotating fan pushing air from the back of a jet engine , or by ejecting hot gases from a rocket engine .