Airplane, Model, is a miniature airplane. It may be a copy of a full-sized plane or have an original design. Building model airplanes is a popular hobby. There are flying and nonflying miniature aircraft of all types, including gliders, helicopters, and commercial and military planes. Scientists also use scale models of aircraft for testing before full-sized planes are built. They test the models in wind tunnels, which duplicate the air pressure and weather conditions of actual flight. See Airplane; Wind tunnel.