Leonardo da Vinci designed ornithopters, flying machines intended to stay aloft by flapping wings through human power.
The word ornithopter comes from Greek roots meaning “bird” and “wing.” Leonardo studied birds extensively and sketched mechanisms in which a pilot would move large wings using pedals, levers, or other body-powered systems. His drawings reflect an effort to imitate biological flight mechanically.
Leonardo's human-powered ornithopters were not demonstrated as successful aircraft. Human muscles cannot generally provide the sustained power needed to flap wings large enough to lift a person, so the designs remained theoretical. They are nevertheless important documents in the history of aviation and biomimetic engineering.
An ornithopter is not the same as a glider. A glider relies on fixed wings and moving air, whereas an ornithopter is defined by flapping wings. Leonardo also explored other flight ideas, but the birdlike flapping-wing designs belong to the ornithopter tradition.