Staff Sgt. Jonathan Bridges, 362nd training squadron instructor, teaches Amn Kevin Castellanos and Amn Jarrett Conklin how to service the pilots breathing oxygen on the B-52 Stratofortress at Sheppard Air Force Base, Texas, Oct. 16, 2017. Castellanos and Conklin are in block six of seven in the B-52 crew chief apprentice course. (U.S. Air Force photo by Alan R. Quevy)