The wing-powered flying-machine concept Leonardo da Vinci studied using a bird-like flapping motion was an ornithopter.
Leonardo filled notebooks with observations of birds, bats, air currents, wings, and the mechanics of flight. An ornithopter imitates a bird by moving wings up and down, rather than relying on a fixed wing or a rotating rotor. His designs included frames, wing membranes, and control ideas intended to transfer human muscle power into flapping motion.
Leonardo correctly recognized that flight required lift and control, but human muscles could not supply enough power for a practical human-carrying flapping aircraft. His machines therefore remained designs and models rather than successful aircraft.
An ornithopter differs from Leonardo’s aerial screw, which used a spiral lifting surface, and from a glider, which uses fixed wings and forward motion. Modern experimental ornithopters can fly with lightweight materials and powered mechanisms, but they are not direct proof that Leonardo’s full-scale designs would have worked.