FAA Sport Pilot Practice Test

An aircraft is any device used or intended for flight in the air. This broad term includes airplanes, helicopters, gliders, balloons, and airships, covering all modes of flight. The other options refer to parts or specific types: the airframe is just the structure of the vehicle, not the whole device; an airship is a particular kind of aircraft that uses buoyancy to stay aloft; and an airplane engine is the propulsion system of an airplane, not the entire flying device. So the best answer is aircraft, because it encompasses any device designed for air travel.