Airman 1st Class Taylor Cook, an electrical and environmental systems apprentice from the 364th Training Squadron, bleeds the air pressure regulator backup valve on top of an F-15 fighter jet at Sheppard Air Force Base, Texas, June 28, 2018. Cook scored 100 on every block test he took throughout his 91 days of training in the aircraft maintnenace specialty. (U.S. Air Force photo by Senior Airman Kevin Clites)