Airman Zion Littlejohn, 362nd Training Squadron crew chief apprentice course student, prepares his tools to perform a maintenance check on an F-16 at Sheppard Air Force Base, Texas, April 10, 2019. It’s a crew chief’s duty to ensure that every component of the aircraft is maintained to the most exacting standards. Littlejohn said the course can be strenuous, but he looks forward to graduating and beginning his career as a crew chief at Nellis AFB, Nevada. (U.S. Air Force photo by Airman 1st Class Madeleine E. Remillard)