One of the most unusual aircraft ever designed for the U.S. Navy was the Chance Vought V-173, also known as the Zimmerman "Flying Pancake". It was a prototype "proof of concept" aircraft that lacked wings, instead relying on its flat circular body to provide the lifting surface. This multi-million dollar project nearly became the first V/STOL (vertical takeoff and landing) fighter. The V-173 blueprints were shown to the Navy in 1939, with wind tunnel tests on full scale models being done in 1940-41. In January 1942 BuAer requested the proposal for two prototype airplanes of an experimental version of the V-173, known as the VS-135. This version had more powerful engines and was given the military designation XF5U-1. Flight testing of the V-173 went on through 1942 and 1943, resulting in reports of "flying saucers" from surprised Connecticut locals. Mock-ups of the XF5U-1 were done in the summer of 1943, but due to Vought's preoccupation with the Corsair and Kingfisher, the program proceeded slowly during the war. The arrival of the jet age saw the cancellation of the XF5U-1 contract by the Navy in March 1947, despite the fact that the aircraft was due to take its first test flight later that year. The XF5U-1 prototype was scrapped, though the V-173 prototype was saved and was given to the Smithsonian. To this day the V-173 / XF5U-1 project remains one of the more interesting anecdotes in aviation history.