The Air Force last year completed a fourth round of upgrades to Boeing's Massive Ordnance Penetrator -- a 30,000-pound bunker-busting bomb designed to hit deeply buried targets -- and established the weapon, the largest conventional explosive in the U.S. military inventory, as a formal program of record, according to a new report. In May 2017, the Air Force successfully completed a three-weapon drop of the MOP at White Sands Missile Range, NM, according to the Pentagon's top weapons tester, which...