Leonardo da Vinci studied an ornithopter as a flapping-wing aircraft intended to achieve human flight.
The word ornithopter means a machine that flies by moving wings like a bird. Leonardo filled several notebooks with observations of birds and bats, along with sketches of wings, frames, joints, and control systems. His designs generally placed a human pilot inside or beneath a lightweight structure and used pedals, levers, or other mechanisms to move the wings.
Leonardo understood that human muscles alone were unlikely to provide enough power for sustained bird-like flight. Even so, his studies were important because they treated flight as a mechanical and scientific problem rather than only as an artistic fantasy. An ornithopter differs from the aerial screw, which relies on a rotating helical surface, and from a glider, which depends on aerodynamic lift without flapping propulsion.