Following the accident, Johnson suggested launching the D-21 from the Boeing B-52 Stratofortress bomber and adding a solid rocket booster to get it up to speed. The drone was modified by adding attachment points on its spine to mate with the carrying pylon on the B-52 and its belly attachment points were adapted to accommodate the rocket booster necessary to increase its speed and allow its ramjet to operate. Its vertical stabilizer was increased in size by approximately 20%. The modified drone version was designated "D-21B" (there was no "D-21A"). Two B-52Hs were modified to carry a pair of drones each by means of two large underwing pylons that replaced the smaller pylons used for the AGM-28 Hound Dog cruise missiles. The tail gunner's and electronic warfare officer's stations were replaced with two launch control stations. Command and telemetry systems were added, and high-speed cameras were installed to track the drones as they separated from the pylons. The launch control officer on the B-52H could communicate with the D-21B and could make it self-destruct.