U.S. Air Force Senior Airman Mason Wyman, 633rd Aerospace Medicine Squadron physiology technician, goes over hypobaric altitude chamber procedures before U.S. Army Rangers go through a series of tests at Langley Air Force Base, Va., Nov. 14, 2014. The chamber tests train and familiarize participants in physiological threats associated with flying. (U.S. Air Force photo by Staff Sgt. Natasha Stannard/Released)