What was found
OMA - DIVERSION - FLT 0012 - APPROXIMATELY 1 HOUR AND 30 MINUTES INTO FLIGHT EN ROUTE FROM PHX TO JFK CREW OXYGEN WENT DOWN TO 20 PSI AND REGULATOR PRESSURE WAS LOW, FLIGHT DIVERTED TO OMA. EMERGENCY OXYGEN SWITCH WAS STUCK IN 100 PERCENT POSITION AFTER GROUND TEST, MASK WAS NOT STOWED PROPERLY CAUSING OXYGEN TO DEPLETE. CONTRACT MAINTENANCE REMOVED AND REPLACED CREW OXYGEN BOTTLE IAW T/C S2A35301, PERFORMED LEAK CHECK, NO LEAKS NOTED.