In February 1961, White unofficially set a new air speed record when he flew the X-15 at a speed of 2,275 mph (3,660 km/h), following the installation of a 57,000 lbf (254 kN) thrust XLR-99 engine. White was the first human to fly an aircraft at Mach 4 and later Mach 5 over the next eight months. On November 9, 1961, White flew the X-15 at 4,093 mph (6,590 km/h), making him the first pilot to fly a winged craft at six times the speed of sound (Mach 6). President John F. Kennedy used the occasion to confer the most prestigious award in American aviation, the Robert J. Collier Trophy, jointly to White and three of his fellow X-15 pilots: NASA's Joseph A. Walker, Commander Forrest S. Petersen of the U.S. Navy, and North American Aviation test pilot Scott Crossfield. A day later, Air Force Chief of Staff General Curtis E. LeMay awarded White his new rating as a Command Pilot Astronaut.