The classical tourbillon, patented by Abraham-Louis Breguet in 1801, holds its rotating cage between two bridges, one below and one above. The upper bridge crosses the visible face of the cage, and partially obscures the view of the mechanism when viewed through the dial. For most of the 19th century this was not a problem, because tourbillons were hidden under pocket-watch dials. When the tourbillon moved to the wristwatch in the late 20th century and manufacturers began cutting dial apertures to show the complication, the upper bridge became a visual obstruction.
Alfred Helwig, a master watchmaker at the Deutsche Uhrmacherschule Glashütte (German Watchmaking School in Glashütte, Saxony), solved the problem in 1920. Helwig engineered the cage to be held only from below, suspended on a single bearing with no upper support, so the cage appears to float. The mechanical challenge is isochronism: without the upper bridge, the cage is less stable on its axis, and the lower bearing must carry both radial and axial loads. Helwig's solution used a reinforced lower bridge and a tightly-tolerated single bearing. His students produced prototypes through the 1920s and 1930s; series production did not begin until the post-war German and Swiss revival of haute horlogerie in the 1960s.
The flying tourbillon is now the dominant variant in modern wristwatch watchmaking. Most contemporary tourbillons, including all A. Lange & Söhne tourbillons (Cabaret Tourbillon, Pour le Mérite, Tourbograph), Glashütte Original's entire tourbillon range, Cartier Astroregulateur, Breguet's modern Classique Double Tourbillon, and Hublot's MP-series flying tourbillons, use Helwig's architecture. The classical two-bridge tourbillon is now the minority position, retained mainly by purists such as F.P. Journe and some Vacheron Constantin Patrimony models.
Modern flying-tourbillon variants include the multi-axis flying tourbillon (Greubel Forsey, Jaeger-LeCoultre Gyrotourbillon), where the cage rotates on two or three axes simultaneously; the central flying tourbillon (Audemars Piguet RD#1), placed at the centre of the dial instead of at 6 o'clock; and the peripheral flying tourbillon where the cage is driven by a peripheral ring rather than a central pinion. Each reduces further the mechanical supports visible to the eye and pushes the "floating cage" effect closer to its logical limit.
