FLC OXYGEN FAILURE AT CRUISE ALT.

Narrative

RPTR FLEW LEAD IN FLT OF 2 SMTP ACFT. ASSIGNED FL290. SHORTLY AFTER REACHING IT; RPTR BECAME HYPOXIC AND PASSED OUT AND WAS NOT AWARE OF ATC; THE #2; AND REAR COCKPIT ATTEMPTING TO COMMUNICATE WITH HIM. PLT IN REAR ADVISED ATC; ZOA THAT HE WAS TAKING THE ACFT TO LOWER ALT AS AN OXYGEN PROB WAS SUSPECTED. RPTR BECAME CONSCIOUS AT FL230 BUT DISORIENTED; WENT TO 100 PERCENT OXYGEN AND SAFETY ON THE REGULATOR AT FL180; THEN TOOK CTL OF ACFT AND CONTINUED FLT AT 18000 FT TO DEST. THE FRONT COCKPIT OXYGEN REGULATOR HAD FAILED AND WILL BE REPLACED. SUPPLEMENTAL INFO FROM ACN 318474: FLT OF (2) LED BY XA T33 SECOND ELEMENT XB VENOM JET; BAKERSFIELD; CA; TO BOISE; ID; AT 29000 FT. DISCOVERED BY RADIO THAT LEAD WAS NOT RESPONDING TO COM. LEADER ACFT BEGAN TO WANDER AROUND; HE TOLD ME TO TAKE LEAD; AND HE CAME INTO THE SLOT POSITION (BEHIND TO 6 O'CLOCK). POS FOR LOST COMS SO I RELAYED TO CTR THAT I WAS #2 IN FLT; I WAS LEVEL 29000 FT. THEY HAD ME SQUAWK MY OWN CODE AND CONTINUE AT 29000 FT TO BOI. VARIOUS ATTEMPTS MADE AT COMMUNICATING WITH XA; AND I BECAME MY OWN FLT TILL LNDG. TURNED OUT THAT PLT HAD LOST OXYGEN AND HIS PAX RECOVERED THE T33 AT 18000 FT IN A HIGH SPD DSCNT. CTR FINALLY ESTABLISHED COM WITH PLT WHO HAD HYPOXIA AT 18000 FT AND I HEARD ON FREQ HE WAS OK. WE BOTH CONTINUED TO BOI UNEVENTFULLY. CORRECTIVE ACTION; OXYGEN TO 100 PERCENT; BUT FIRST MUST RECOGNIZE LOST OXYGEN.