Leonardo da Vinci sketched an ornithopter as a flying machine with flapping, bird-like wings.
His studies of birds and bats led him to imagine a craft powered by wing motion rather than by a propeller or engine. Several notebooks contain drawings of wing frameworks, harnesses, and mechanical systems intended to transfer human effort to the wings.
Leonardo’s ornithopter was never built as a successful human-powered aircraft. The main difficulty was that a person could not produce enough sustained power to lift the machine and its pilot. Modern ornithopters use motors, while Leonardo’s design belonged to Renaissance mechanical speculation rather than practical aviation.