Airman Jacob Blann, sitting, and Airman Isaiah Herring, 362nd Training Squadron KC-135 crew chief apprentice course students, service a KC-135 Stratolifter at Sheppard Air Force Base, Texas, Dec. 13, 2018. The students are servicing the main landing gear so the springs and hydraulic fluid will allow the plane a smoother landing. If not done often, the landing gear will grow stiff, endangering the pilots and crew members when the aircraft attempts to land. (U.S. Air Force photo by Airman 1st Class Pedro Tenorio)