U.S. Air Force Gen. Jeffrey L. Harrigian, U.S. Air Forces in Europe and Air Forces Africa commander, coins U.S. Air Force Airman 1st Class Maria G. Naranjo, 606 Air Control Squadron tactical data link system technician, at Aviano Air Base, Italy, Nov. 15, 2019. The challenge coin tradition began in World War I and exhibits commendable service, a lively legacy and supports unit morale across the Air Force. (U.S. Air Force photo by Airman Thomas S. Keisler IV)