What was found
AIRCRAFT PERFORMED AN UNSCHEDULED LANDING DUE TO DURING CRUISE AT 38,000 FEET, THE CREW OXYGEN LOW LIGHT TURNED ON. PERFORMED AN OXYGEN CREW INSPECTION IAW AMM 35-12-85, DETECTING OXYGEN BOTTLE MANOMETER WAS INDICATED 0 PSI. THE OXYGEN BOTTLE WAS REPLACED IAW AMM DMC-B787-A-12-15-08-00B-200A-A, TESTED CORRECT.