Major Daniel Gibson, 779th Aerospace Medicine Squadron aerospace and operational physiology training flight commander, observes as flight 1626 gives a thumbs up to indicate they are breathing normally and ready to proceed with training in the altitude chamber at Joint Base Andrews, Md., March 18, 2010. The physiology training flight trains aviators and special operations high-altitude parachutists how to recognize physiological stresses and human performance factors associated with military flying, and more importantly, how to overcome these challenges. (U.S. Air Force photo by Senior Airman Katie Spencer)