1 contradicts the claim, contending for Welch's aircraft to break the sound barrier with an underpowered engine was impossible. He notes that the XP-86 airframe was capable of transonic flight, but the interim low-power J35-C-3 limited its performance. The late Bob Hoover, chase pilot for Welch and Yeager, had also disputed the Welch story, stating that Welch was not flying that day because his plane was being repaired. The highest Mach number reached by Welch in 1947, as indicated by official flight test records, was about 0.93, in a maximum power dive from with the engine at 100.8% Military RPM (i.e. maximum power). North American conducted this test, their "High Mach Number Investigation", on November 13. The USAF verified all North American results and this test Mach number in their own Phase II tests conducted in December 1947. By the end of 1947, the XP-86 had logged 29 hours and 23 minutes of flight test time, most flown by Welch. On October 14, 1947, Captain Charles Yeager exceeded Mach 1 in the Bell X-1. The claim of the XP-86 passing Mach 1, with Welch at the controls, was not made until April 26, 1948, five and a half months after the X-1 supersonic flight. Blackburn, however, maintains that a record on the Muroc radar theodolite, of the two flights Welch made on November 13, 1947, indicated supersonic flights, as well, noting 20 minutes before the X-1 broke the record, a sonic boom was heard over the desert, centered on the Happy Bottom Riding Club, dude ranch restaurant and hotel operated by Pancho Barnes. Later career and death Welch went on to work as chief test pilot, engineer, and instructor with North American Aviation during the Korean War, where he reportedly downed several enemy MiG-15 Fagots while "supervising" his students. Welch's kills were in disobedience of direct orders for him not to engage, and credits for the kills were thus distributed among his students. After the war, Welch returned to flight testing; this time in the F-100 Super Sabre, with Yeager flying the chase plane. Welch became the first man to break the sound barrier in level flight with this type of aircraft on May 25, 1953. Stability problems were encountered in the flight test program, and on Columbus Day, October 12, 1954, Welch's F-100A-1-NA Super Sabre, AF Ser. No. 52-5764, disintegrated during a 7-G pullout at Mach 1.55 from 45,000