North-American-Aviation-X-15-and-B-52 Published on March 9, 2019 in 10 March 1959Full resolution (1150 × 901) ← Previous 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)