Leonardo da Vinci sketched an ornithopter as an aircraft with flapping wings inspired by birds.
The word ornithopter combines Greek roots meaning “bird” and “wing.” Leonardo studied bird flight, wing movement, balance, and the relationship between lift and body weight while developing several flying-machine designs in his notebooks.
His ornithopter concepts were human-powered: the pilot would use mechanical levers and pedals to move the wings. They were never proven capable of sustained flight, because human muscles cannot provide enough power for a practical flapping aircraft of that size. Leonardo also designed gliders and a separate aerial screw, so these ideas are often confused.
Modern ornithopters do exist as small experimental aircraft and robotic devices, but they generally use motors rather than a person’s muscles. Leonardo’s work remains historically important because it applied close observation of nature to the engineering problem of flight.