Tech. Sgt. Ryan Castle, 363rd Training Squadron F-16 aircraft armament systems apprentice course instructor, watches as students from his class prep a BRU-57/A sub-rack for removal. The sub-rack allows the pylon to hold two munitions that can weigh up to 1,000 pound each, instead of just one. Castle's students are on block eight of 12 and are scheduled to graduate on Jan. 3, 2018. (U.S. Air Force photo by Alan R. Quevy)