U.S. Air Force Staff Sgt. Matthew Shoup, 355th Civil Engineer Squadron explosive ordnance disposal technician, assesses and marks simulated unexploded ordnance during a training exercise at Davis-Monthan Air Force Base, Ariz., March 28, 2018. The exercise involved the discovery, assessment and disposal of unexploded ordnance on a mock runway. (U.S. Air Force photo by Airman 1st Class Michael X. Beyer)