Leonardo da Vinci’s bird-inspired flying-machine concept is called an ornithopter.
An ornithopter is an aircraft intended to fly by flapping wings, imitating the motion of birds or bats. Leonardo made many studies of bird flight and designed machines in which a person would operate large wings through mechanical linkages. His notes examined wing shapes, balance, muscles and the relationship between weight and lift.
Leonardo’s ornithopter designs did not become practical aircraft. A human pilot could not produce enough power through arm and leg movements to lift a machine of the proposed size. Modern aircraft generally use fixed wings or powered rotors instead, because those systems produce lift more efficiently for human-scale vehicles.
The ornithopter is often confused with Leonardo’s aerial screw. The aerial screw depended on a rotating helical surface, while the ornithopter depended on flapping wings. Leonardo’s work remains important because he approached flight through observation and mechanical analysis rather than treating it only as a fantasy.