An ornithopter is an aircraft that flies by flapping its wings. Designers sought to imitate the flapping-wing flight of birds, bats, and insects. Though machines may differ in form, they are usually built on the same scale as flying animals. Larger, crewed ornithopters have also been built and some have been successful. Crewed ornithopters are generally powered either by engines or by the pilot.

Alphonse Pénaud, was a 19th-century French pioneer of aviation design and engineering. He was the originator of the use of twisted rubber to power model aircraft, and his 1871 model airplane, which he called the Planophore, was the first aerodynamically stable flying model. He went on to design a full-sized aircraft with many advanced features, but was unable to get any support for the project, and eventually committed suicide in 1880, aged 30.