Leonardo da Vinci studied the ornithopter, a flying-machine concept propelled by flapping wings.
The word ornithopter comes from Greek roots meaning bird-winged. Leonardo examined birds and bats, then sketched mechanisms intended to imitate their wing motion. His notebooks include several approaches, including machines powered by a pilot's arms and legs and others using mechanical transmission systems.
Leonardo understood that human muscle power would probably be insufficient for a full-sized flapping aircraft. Even so, his investigations were important because they treated flight as a mechanical and anatomical problem rather than as a purely fantastical idea.
An ornithopter is not the same as a helicopter or a glider. A helicopter generates lift with rotating blades, while a glider relies on aerodynamic lift without powered flapping. Modern experimental ornithopters have flown, but Leonardo's proposals were never documented as successful human-carrying aircraft.