Sheet metal mechanics Alex Turbyfill, right, and Gilbert Martinez, assigned to 533rd Commodities Maintenance Squadron, work on an F-16 wing April 26, 2018, at Hill Air Force Base, Utah. The 533rd is performing structural-strengthening modifications as part of the F-16 Service Life Extension Program, or SLEP, that will keep the jets flying for decades. (U.S. Air Force photo by R. Nial Bradshaw)