Airman Denver Bobbitt, 362nd Training Squadron C-130 crew chief apprentice course student, services a C-130 Hercules at Sheppard Air Force Base, Texas, Nov. 1, 2018. Bobbitt is learning how to service the C-130's liquid oxygen, which provides the pilots and the aircrew oxygen while at high altitudes. (U.S. Air Force photo by Airman 1st Class Pedro Tenorio)