U.S. Air Force Senior Airman Sean Keriston, 42nd Aerial Port Squadron, Westover, Mass., works on the flight-line at Schoonover Airfield, Fort Hunter Liggett, Calif., May 19, 2011, while participating in Exercise Global Medic 2011 and Warrior 91 11-01. Global Medic is a joint field training exercise for theater aeromedical evacuation system and ground medical components designed to replicate all aspects of combat medical service support. Warrior Exercise gives participating units an opportunity to rehearse military maneuvers and tactics such as security, convoy operations and quick reaction drills during simulated enemy attacks.