High-altitude contrails frame the B-52 mothership as it carries the X-15 aloft for a research flight on 13 April 1960 on Air Force Maj. Robert M. White’s first X-15 flight.

Note the black contrails commonly seen from the eight engines of the B-52. Despite its age, the B-52 is still regularly flown and kept in prime combat readiness. Part of the reason for its long ...