Two Washington, D.C., Air National Guard F-16 Fighting Falcons roll towards the flightline for during a simulated alert mission at the 113th Fighter Wing’s Aerospace Control Alert Detachment, Joint Base Andrews, Md., March 30, 2015. The alert unit was created in response to the September 11, terrorist attack on the United States in 2001. (U.S. Air Force photo/Airman 1st Class Philip Bryant)