ELMENDORF AIR FORCE BASE, Alaska—Crew Chiefs from Kadena Air Base, Japan, conduct the pre-flight checklists on F-15 Eagles Elmendorf Air Force Base, Alaska, May 13. The F-15s from Kadena are participating in Northern Edge, a joint service exercise designed to test military capabilities if a crisis occurs. The F-15 is a tactical fighter designed to gain and maintain air superiority. (U.S. Air Force Photo by Airman 1st Class Jonathan Steffen)