Leonardo da Vinci designed an ornithopter, an aircraft intended to fly by flapping wings inspired by birds and bats.
His notebooks contain numerous studies of bird flight, wing structure, balance, and the movement of air. Several designs place a pilot inside a framework who would operate wings through pedals, levers, or other mechanical parts.
An ornithopter is different from an airplane: an airplane uses fixed wings and forward motion to generate lift, while an ornithopter seeks lift and thrust through flapping wings. Leonardo’s proposals were never practical human-powered aircraft because human muscles cannot provide enough sustained power for such a machine.
Modern experimental ornithopters have flown, especially small radio-controlled models. Leonardo’s work is important mainly because it combined close observation of animals with mechanical design, rather than because one of his full-sized machines flew.