Leonardo da Vinci’s bird-inspired flying-machine concepts are known as ornithopters.
An ornithopter is an aircraft intended to fly by flapping wings, rather than by using fixed wings or a rotary rotor. Leonardo studied birds and bats extensively and produced several designs in the late fifteenth and early sixteenth centuries. His sketches explored wing structures, frames, and mechanisms for transferring human power to flapping wings.
Leonardo’s human-powered ornithopters were not practical aircraft because a person could not generate enough power for sustained flapping flight. The designs nevertheless influenced the history of aviation by treating flight as an engineering problem involving lift, weight, structure, and motion. Modern ornithopters have been built experimentally, often using motors or remote control.