Leonardo da Vinci's proposed flapping-wing flying machine was an ornithopter.
The word ornithopter means a craft that flies by flapping wings, imitating the motion of birds or bats. Leonardo studied bird flight extensively and produced several designs in the late fifteenth and early sixteenth centuries. His concepts generally placed a human pilot in a frame connected to large wings through levers, pedals, or other mechanical linkages.
Leonardo recognized that human muscle power alone would probably not be enough to sustain flight with a bird-like machine. Some of his notes therefore explored gliding, mechanical assistance, and the anatomy of wings. None of his ornithopters is known to have flown successfully.
The term is often confused with Leonardo's aerial screw, which used a rotating helical surface rather than flapping wings. Leonardo's studies still influenced later thinking about aerodynamics, even though powered human flight required engines and materials unavailable in his time.