Leonardo da Vinci sketched an ornithopter, an aircraft intended to fly by flapping wings.
His Codex Atlanticus and other notebooks contain studies of bird anatomy, wing movement, and air resistance. Leonardo reasoned that a flying machine should imitate the lift and propulsion produced by birds, although his proposed human-powered designs could not generate enough energy for sustained flight.
An ornithopter is defined by flapping wings, not by the shape of its body. That distinguishes it from a glider, which relies on fixed wings, and from a helicopter, which uses rotating blades. Leonardo’s drawings are important early investigations into aeronautical engineering, even though none of his full-sized flying machines is known to have flown.
The word “ornithopter” comes from Greek roots meaning “bird” and “wing.” Modern experimental ornithopters have been built, but they are not evidence that Leonardo’s original designs were practical.