North American Aviation X-15 and B-52 Published on August 4, 2012 in 4 August 1960Full resolution (1150 × 1024) Next → North American Aviation X-15A 56-6670 carried aloft by Boeing NB-52A Stratofortress 52-003. The absence of frost on the fuselage of the X-15 shows that no cryogenic propellants are aboard for this captive flight. (NASA)