Bell Aircraft began studying the tilt rotor concept in the 1940s. The XV-3 was the first hardware to come out of the design work and led to the V-22 Osprey (via the Bell XV-15 tilt rotor). Two XV-3s were built between 1952 -55, with the first (54-147) crashing in 1956 during testing. The cause was in-flight instability and the remaining aircraft continued extensive flight and wind tunnel testing. This aircraft was retired in 1966 after being damaged during the last wind tunnel test. It was transferred to the National Museum of the US Air Force in 2007 after a two year restoration by Bell.