Dropped in mid-air from beneath the wings of a B-52 mothership, the X-15 A-2 ignited its powerful rocket engine and streaked into the upper-atmosphere.
Previous burns only lasted 90-seconds, but on this October 3, 1967, flight, the aircraft was equipped with special tanks that would allow the rocket to stay lit for an additional 51-seconds. The additional burst of thrust sent the X-15 A-2 hurtling through the sky to reach a speed of Mach 6.70. As the engine burned out, alarms sounded and the plane was buffeted by shockwaves. Aerodynamic heat melted an attachment pylon and tore-away a dummy scramjet that was being tested on the aircraft.
It was the fastest speed at which a piloted flight had flown, and with the mission having come perilously close to disaster, the record has not been challenged to this day…
Source: YouTube