A 362nd Training Squadron KC-135 crew chief apprentice course instructor shows his class how to open the doors on a KC-135 Stratotanker at Sheppard Air Force Base, Texas, Sept. 27, 2018. The class, on their fourth day of training, must learn the basics of the aircraft first before learning the more complicated ins and outs of one of the most important aircraft in the Air Force's arsenal. (U.S. Air Force photo by Airman 1st Class Pedro Tenorio)