What was found
FLT 0820 - WHILE EN ROUTE FROM BOS TO PHX CREW OXYGEN WENT TO ZERO, DIVERTED TO ROC. MAINTENANCE REMOVED AND REPLACED THE CREW OXYGEN BOTTLE IAW AWA T/C R2A35301. PERFORMED LEAK CHECK OF ALL CONNECTIONS AT BOTTLE, ALSO CHECK ALL MASKS FOR CORRECT STOWAGE AND LEAKS, NO LEAKS NOTED DURING 2 HOUR PERIOD.