Leonardo da Vinci designed an ornithopter, a flight machine intended to fly by flapping wings.
The name combines Greek words meaning bird and wing. Leonardo filled notebooks with observations of birds, bats and the mechanics of wings. His proposed machines used human or mechanical power to move large wings, reflecting his belief that careful study of nature could guide engineering.
Leonardo’s ornithopters were designs rather than successful aircraft. Human muscles could not provide enough power for a machine of the proposed size, and the mechanisms could not reproduce the complex aerodynamics of a living bird. The concept nevertheless became an important milestone in the history of attempts at powered flight.