2004: In its final flight, NASA’s B-52 #008 launch vehicle, the oldest plane in the USAF inventory, carries the X-43A mounted on a Pegasus booster into the air. The X-43A breaks its 4,780 MPH record of 27 March 2004. After separating from a Pegasus booster rocket at 110,000 feet, the scramjet engine accelerates the X-43 to 7,000 mph (Mach 9.8).