North American Aviation X-15s 56-6670 and 56-6671, with NB-51A 52-003 and NB-52B 52-008, ready for takeoff, 4 November 1960 Published on November 16, 2012 in 4 November 1960Full resolution (1600 × 1200) Next → At the left, Boeing NB-52A 52-003 carries X-15 56-6670 while on the right, NB-52B 52-008 carries X-15 56-6671.(NASA)