191115-F-KN521-0016 An F135 engine sits in an Arnold Engineering Development Complex (AEDC) Engine Test Facility (ETF) test cell at Arnold Air Force Base, Tennessee between test runs. The F135 is undergoing Accelerated Mission Testing in the AEDC facility. It is one of two engines used to power the F-35 Joint Strike Fighter Lightning II. (U.S. Air Force photo by Jill Pickett) 2020.02.03