Leonardo da Vinci sketched an ornithopter as a flying device with wings designed to flap like a bird’s.
The word ornithopter comes from Greek roots meaning “bird” and “wing.” Leonardo studied birds extensively and tried to understand how their wings generated lift and thrust. His designs generally used a human operator’s muscle power to move large wings.
Leonardo’s drawings were imaginative engineering studies rather than working aircraft. Human muscles cannot produce enough sustained power to lift a person with flapping wings of the proposed size. Modern ornithopters use engines or other mechanical power sources, and some small unmanned examples have flown.
An ornithopter is different from Leonardo’s other famous aviation sketches. His aerial screw proposed rotary lift, while his parachute used a canopy to descend safely. Those concepts are often grouped together, but they represent different approaches to flight.