 With the loss of the X-2, the search for many of the answers to the riddles of high-Mach flight had to be postponed until the arrival of the most ambitious of the rocket planes—the North American X-15.Meanwhile, the turbojet revolution had reached a high plateau at Edwards.By the time the base was officially designated the U.S. Air Force Flight Test Center in June 1951, more than 40 different types of aircraft had first taken flight at the base and the nation's first generation of jet-powered combat airplanes had already completed development.