What was found
WHILE AT CRUISE FL350, THE FLT DECK HALON FIRE EXTINGUISHER SPRUNG AN UNCONTROLLABLE LEAK. THE FLIGHT CREW DONNED THEIR O2 MASKS. A JUMPSEAT PILOT REMOVED THE EXTINGUISHER FROM THE COCKPIT AND MOVED IT INTO THE FORWARD LAVATORY. THE LAVATORY REMAINED CLOSED UNTIL THE EXTINGUISHER FULLY DISCHARGED. IT WAS THEN REMOVED, PLACED IN A BAG AND STORED IN THE FORWARD CLOSET. A SUBSTITUTE FIRE EXTINGUISHER WAS MOVED INTO THE FLIGHT DECK. THE FLIGHT CONTINUED TO DESTINATION WITHOUT FURTHER INCIDENT. THE FIRE EXTINGUISHERS WERE REPLACED IN BOTH THE F/C EQUIPMENT BAY AND THE FLIGHT DECK IAW AMM 26-26-01-401 AND AMM 26-26-02, OK FOR SERVICE. THE AIRCRAFT WAS NOT GROUNDED.