Leonardo da Vinci created ornithopter concepts by studying the wing movements of birds and bats.
An ornithopter is an aircraft intended to fly by flapping wings, rather than by using fixed wings, rotors, or lighter-than-air gas. Leonardo filled notebooks with observations of bird flight, wing structure, balance, and the movement of air. His proposed machines used human power to move wings mechanically.
Leonardo understood that human muscles could not provide enough power for a person-sized flapping aircraft. Some designs therefore included mechanical systems, although none became a working aircraft. The word ornithopter comes from Greek roots meaning bird and wing.
Leonardo’s sketches are historically important because they treated flight as an engineering problem based on anatomy and mechanics. They were not blueprints for a successful airplane, and claims that he built a flying machine are unsupported. His studies nevertheless influenced later attempts to imitate animal flight.