What was found
AIRCRAFT PERFORMED AN UNSCHEDULED LANDING AT JFK DUE TO CREW OXYGEN CYLINDER WITH LOW PRESSURE AND DURING CRUISE AT 37,000 FEET AND THE OXYGEN PRESS DROPS 250 PSI WITH 1 HR. MAINTENANCE PERSONNEL PERFORMED AN OXYGEN CREW INSPECTION IAW AMM 35-12-85, DETECTING OXYGEN BOTTLE MANOMETER WAS INDICATED 0 PSI; SO THE OXYGEN CYLINDERS WERE REPLACED AND LEAK CHECK WAS PERFORMED IAW DMC-B787-A-12-15-08-00B-200A-A, TESTED CORRECT. THE OVERWEIGHT LANDING CONDITION INSPECTION WAS NOT NECESSARY DUE TO THAT THE LANDING CONDITION VALUES WERE WITHIN LIMITS IAW DMC-B787-A-05-51-01-00B-311A-A, TABLE 5, ALL CORRECT.