Massive Ordnance Penetrators

The GBU-57 series MOP—the initials stand for Guided Bomb Unit and Massive Ordnance Penetrator—is a 30,000-pound (14,000 kg) class, 20.5-foot-long (6.2 m) precision-guided munition "bunker buster" bomb developed by Boeing for the United States Air Force (USAF). Composed of a BLU-127 bomb body and an integrated GPS/INS guidance package, the GBU-57 has seven variants, the most recent being the GBU-57F/B. Due to its size and weight, the GBU-57 MOP can be carried only by the Northrop B-2 Spirit strategic bomber and the B-21 Raider, although initial tests were conducted with a modified Boeing B-52 Stratofortress.