Leonardo da Vinci sketched an ornithopter, a machine with flapping wings intended to imitate the flight of birds or bats.
The word ornithopter comes from Greek roots meaning bird and wing. Leonardo studied bird anatomy, wing movement, air currents, and the relationship between weight and lift. His flying-machine drawings included mechanisms in which a human pilot would move wings through pedals, levers, or other mechanical linkages.
Leonardo understood that human muscle power alone would make sustained flapping flight extremely difficult. None of his ornithopter designs is known to have flown successfully, and many were too heavy or mechanically demanding for a person to operate.
An ornithopter differs from a glider, whose wings remain fixed while it descends or rides air currents. It also differs from Leonardo's aerial screw, which proposed rotary motion. The ornithopter's defining feature is powered flapping wings.