He went on to fly the prototypes of the Navy's North American FJ-1 and later the Army Air Forces' XP-86. North American originally proposed a straight-wing version of the XP-86 and the Army Air Forces accepted this on May 1, 1945. On November 1, North American, with the aid of captured German technology, proposed and was given permission for a major redesign of the XP-86 to a 35-degree, swept-wing configuration. This was new technology and the USA's first high-speed, swept-wing airplane and a significant advance over Republic Aviation's XP-84. Welch was chosen as chief test pilot for the project. In September 1947, the first of three XP-86 prototypes (AAF Ser. No. 45-59597) was moved from North American's Mines Field (later Los Angeles International Airport) to the Muroc North Base test facility (now Edwards AFB), the same base at which the Bell X-1 was being tested. The maiden flight of the XP-86 was on October 1, 1947, flown by Welch. After about a 30-minute flight, Welch lowered the flaps and gear to land. At this point, the nose gear would not extend completely. For 40 minutes, Welch unsuccessfully tried everything to extend the nose gear. When he reached a low-fuel state, he elected to land on Muroc Lake Bed without a fully extended nose gear. Upon touchdown, in a nose-high attitude, Welch cut the engine, and as the XP-86 slowed, the nose gear snapped down and locked. The aircraft was undamaged. Secretary of the Air Force Stuart Symington had instructed North American that they were not, under any circumstances, to break the sound barrier before the X-1 achieved this milestone. He could exercise his authority in this regard because both the XP-86 and X-1 were Air Force programs. Welch's only complaints about the aircraft was the J35 engine lacked power and the rate of climb was only a disappointing per minute. North American, however, had already contracted with General Electric for more powerful J47 engines for the production P-86As. In his book Aces Wild: The Race for Mach 1 (1998), fellow North American test pilot Al Blackburn speculates that Welch may have broken the sound barrier 2 weeks before Chuck Yeager in an early flight of the XP-86 prototype. Welch himself never made that claim. Blackburn based his contention on interviews of eyewitnesses, former North American employees, and access to contemporary historical accounts. Robert Kempel, author of The Race For Mach