This week in Edwards history Published Jan. 3, 2018 By 412th Test Wing Public Affairs EDWARDS AIR FORCE BASE, Calif. -- On Jan. 3, 1966, the second prototype of the XB-70 achieved a speed of Mach 3.05 at 72,000 feet, marking the first time the aircraft type had flown at three times the speed of sound. This Edwards History Office file photo was taken June 8, 1966.