Leonardo da Vinci's wing-flapping aircraft was an ornithopter. The term combines Greek words meaning “bird” and “wing,” and it describes an aircraft intended to fly by flapping wings like a bird or insect.
Leonardo filled his notebooks with studies of bird flight, wing structure, airflow, and the movement of muscles. His ornithopter sketches included large wings operated by human power through pedals, levers, and other mechanical linkages. He understood that a flying machine would need both lift and propulsion, but he underestimated how much power a human could produce.
Leonardo never demonstrated a successful man-powered ornithopter. His designs are therefore important as investigations into flight rather than as working aircraft. An ornithopter is also different from a glider: a glider gains lift while moving through air without flapping, whereas an ornithopter depends on oscillating wings for its intended propulsion.