Leonardo da Vinci's ornithopter was a human-flight machine designed with flapping wings. The term comes from Greek words meaning “bird” and “wing,” and Leonardo studied bird anatomy and flight to develop several versions.
His notebooks include wing mechanisms operated by a pilot's arms and legs, along with observations about lift, balance, and air resistance. Leonardo believed a sufficiently strong person might imitate a bird by moving large wings, but the available materials and human muscle power could not produce enough lift for sustained flight.
Unlike a glider, an ornithopter depends on powered flapping rather than simply riding air currents. Leonardo's designs were never tested successfully, and no complete machine survives. Nevertheless, his investigations helped establish a systematic approach to aerodynamics based on observation.
Modern ornithopters use engines or lightweight mechanisms, and small models can fly. They demonstrate the principle, but they should not be confused with Leonardo's unpowered human-scale proposals.