Leonardo da Vinci sketched an ornithopter, an aircraft intended to fly by flapping wings inspired by birds and bats.
Leonardo filled notebooks with studies of bird flight, wing shapes, muscles, balance, and air currents. Those observations informed several proposed flying machines in which a human pilot would operate wings mechanically. The general category for such a flapping-wing aircraft is an ornithopter.
His designs were not powered by an engine and were unlikely to have lifted a person using Renaissance materials and human muscle alone. Leonardo’s work nevertheless helped connect close observation of animals with engineering design.
An ornithopter should not be confused with a glider, which depends on aerodynamic lift without flapping wings. It is also distinct from Leonardo’s aerial screw, which used a rotating helical surface rather than birdlike wings.