Leonardo da Vinci studied an ornithopter, a flying machine intended to fly with flapping wings.
The word ornithopter means a craft that flies by the movement of wings, rather than by fixed wings or a balloon. Leonardo investigated bird and bat anatomy, wing movement, air resistance, and the mechanics needed to transmit a pilot’s effort to wings. His surviving notebooks contain several versions of flapping-wing machines.
Leonardo’s studies were analytical as well as imaginative. He recognized that a human pilot would probably lack the strength needed to flap wings large enough for sustained powered flight. Some designs used pedals, levers, and other mechanisms, but none is known to have flown successfully. The famous term “flying machine” can refer to several Leonardo designs, so “ornithopter” is the more specific category.
Leonardo also studied gliding devices, including a wing-like apparatus. Those should not be automatically classified as ornithopters, because a glider has fixed wings and does not depend on flapping motion.