U-2 pilots undergo hour of pure oxygen before high-altitude missions

Before takeoff, pilots of the Lockheed U-2 Dragon Lady reconnaissance aircraft spend a full hour breathing pure oxygen. The preparation protects them during missions that can last nine to eleven hours at altitudes near 70,000 feet.

The aircraft, which flies out of Beale Air Force Base, keeps a cabin altitude of around 29,000 feet in flight. According to the report, that pressure level puts pilots at risk of problems similar to those faced by scuba divers who surface too quickly, including decompression sickness.

Breathing pure oxygen beforehand purges nitrogen from the bloodstream. That lowers the chance of gas bubbles forming as pressure changes during ascent. The report describes the procedure as a standard part of preparing for U-2 sorties, missions known for taking a heavy physical toll on crews given the extreme altitude and long duration.

The U-2 has flown for decades and still carries out intelligence, surveillance, and reconnaissance missions. Operating at the edge of the atmosphere has long demanded pilot protocols beyond those used in conventional aviation, including full-pressure suits similar to those worn by astronauts.

The report describes no new incident and no change in procedure. It documents existing, long-standing practice for U-2 operations rather than a recent development.