The flying tourbillon is a variation of the tourbillon pioneered by Abraham-Louis Breguet. Rather than being supported by a bridge, or cock, at both the top and bottom, it is cantilevered, being only supported from one side. The first flying tourbillon was designed by Alfred Helwig, instructor at the German School of Watchmaking, in 1920^*.

Links:

Article on Alfred Helwig by the modern Glashutte-Original company

Article on the world's most complicated wristwatch, centering on the flying tourbillon