U.S. Air Force Staff Sgt. Heather Doyle, 9th Physiological Support Squadron launch and recovery technician, fits a specialized boot to U-2 pilot Capt. Travis, in preparation for a "high flight" at Beale Air Force Base, Calif., Jan. 8, 2013. Since its inception in 1955, the U-2 has required the use of a pressure suit to regulate the pressure for pilots above 50,000 feet. The U-2 is the only aircraft in the Department of Defense inventory that requires the utilization of a full pressure suit. (U.S. Air Force photo by Airman 1st Class Drew Buchanan/Released)