Leonardo da Vinci studied an ornithopter as a possible way for humans to fly by flapping wings.
An ornithopter is an aircraft designed to fly through the motion of wings, much as birds and bats do. Leonardo filled his notebooks with observations of birds, wing structures, balance, and air movement. Those studies informed several flying-machine sketches, including machines in which a person would operate wing mechanisms.
Leonardo understood that human muscles could not simply reproduce the power of a large bird. His designs therefore explored levers, pedals, and other mechanical arrangements to magnify the pilot’s effort. None of the known designs produced a documented human-powered flight.
The term should not be confused with Leonardo’s aerial screw, a separate rotating-wing concept often compared with a helicopter. Leonardo’s flying studies were important for the history of aeronautical thinking, but his machines remained designs and experiments rather than practical aircraft.