North American Aviation X-15 56-6670 with Boeing NB-52A Stratofortess 52-003, first USAF flight, Robert M. White 13 April 1960 Published on August 12, 2012 in 13 April 1960Full resolution (1141 × 786) ← Previous X-15 56-6670 with NB-52A 52-003, 13 April 1960. (NASA)