In 1947, based on the German Lippish's delta wing design, Douglas designed and produced an excellent Douglas F4D-1 Skyray. After Five years of its operation, Douglas engineers collected the weakness and created a new improved fighter, the Douglas F4D-2N. The U.S. Navy interested the concept, two prototypes was ordered to Douglas. As it was actually very different with the Douglas F4D-1 Skyray, although it was outwardly similar, a new designation F5D-1 Skylancer was given. The F5D-1 was powered by the same engine as used in Douglas F4D-1. During its first flight in 1956, it exceeded sound speed easily. The F5D-1 was judged an outstanding interceptor but lost production contract to the Vought F8U-1 Crusader by political motives rather than the technical reasons. It was because Douglas had many military airplane orders from the Navy at that time. After Navy's cancellation, four airplanes were proceeded with various Military tests until 1961. Then two were grounded and two transferred to NASA. It was finally retired in 1970.