Staff Sgt. Ryan Lindsey, 362nd Training Squadron airlift instructor, trains his students on servicing a C-130 Hercules with liquid oxygen May 27, 2015, at Sheppard Air Force Base, Texas. The liquid oxygen is extremely cold with a boiling point of negative 297 degrees Fahrenheit and will be a part of the Airmen's everyday tasks when they graduate technical school and join operational flight lines across the Air Force. (U.S. Air Force photo by Danny Webb/ Released)