As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCI - DIVERSION - FLT 0285 - EN ROUTE FROM ORD TO PHX CREW OXYGEN LEAKED DOWN TO 60 PSI, DIVERTED TO MCI AND LANDED WITHOUT FURTHER EVENT. MAINTENANCE FOUND THE OBSERVERS MASK STOWED INCORRECTLY ALLOWING OXYGEN TO ESCAPE, RE-STOWED OBSERVERS MASK TO CORRECT POSITION, AND REPLACED CREW OXYGEN BOTTLE.