Bell's X-5 caught against something closely resembling a lunar landscape that turns out to be an area just north of Edwards AFB. Based on the Messerschmitt P.1101 interceptor that had a three-position, variable sweep angled wing that required setting before each flight. Bell took the concept on a stage, providing an in-flight adjustable sweep range from 20 to 60 degrees, compared with the P.1101's 35 to 45 degree movement. Two X-5s were built for the US Air Force, 50.1838 and 50.1839, the type's first flight being made on 20 June 1951. The second machine was destroyed when it spun in on 14 October 1953, fatally injuring Major Raymond Popson. Above is a revealing ground view of the surviving X-5, 50.1838. The inherent flexibility of the underslung engine mounting was one emphasised by Bell as permitting real choice of engine fit when they came to push the US Air Force to consider buying a fighter development of the X-5. The US Air Force rejection of this proposal was based on the overall small size of the X-5. The X-5"s final flight was made on 25 October 1955, by no less a future luminary than Neil Armstrong.