The Platt LePage XR-1 was the winner of a design competition for a contract for the United States Air Force. This was the very first helicopter flown by the USAF, actually the USAAF. The prototype here flew in 1941 and was retired from flight testing in 1945. Malfunctions, a test flight crash and instability problems plagued the XR-1. This was not a challenging problem for the US as newer an d better rotorcraft were being developed. So it was cancelled. It did feature huge observation windows that has stayed with helicopter design until today.