Narrative:

After departure from aua; about 2.5 hours into flight; a check of the crew oxygen supply pressurization revealed complete loss. As per procedures; we (first officer and myself) immediately offset 15 mi west of airway while descending to FL250. New york radio was also advised of our situation by HF radio. Closest airports; being over 400 mi to sea; were NAS; pls; fpt. I chose; of course; to continue to mia; not being in an emergency condition. An emergency was not declared. #1 flight attendant was quick to bring 2 walkaround bottles for us up front (not used). ZNY cleared us direct to mia via HF. First officer was also very busy with dispatch with situation; divert; crew legality; maintenance and fuel requirements; etc. After docking at gate; mia maintenance was on the aircraft right away; found that a previous jumpseat rider had improperly stowed a mask; that at some point in-flight bled the tank dry. Tank was replaced and leak tested. Here's more: IRS deviation was extremely excessive at 56-80 mi off. Seems the #3 IRS went south. Mia avionic technicians got on this simultaneously and replaced the complete gyro platform.

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Original NASA ASRS Text

Title: ACR CREW DISCOVERS CREW OXYGEN IS DEPLETED AT FL340 WHILE FLYING IN NEW YORK OCEANIC AIRSPACE. THEY DSND TO FL250 AND CONTINUED TO MIA.

Narrative: AFTER DEP FROM AUA; ABOUT 2.5 HRS INTO FLT; A CHK OF THE CREW OXYGEN SUPPLY PRESSURIZATION REVEALED COMPLETE LOSS. AS PER PROCS; WE (FO AND MYSELF) IMMEDIATELY OFFSET 15 MI W OF AIRWAY WHILE DSNDING TO FL250. NEW YORK RADIO WAS ALSO ADVISED OF OUR SITUATION BY HF RADIO. CLOSEST ARPTS; BEING OVER 400 MI TO SEA; WERE NAS; PLS; FPT. I CHOSE; OF COURSE; TO CONTINUE TO MIA; NOT BEING IN AN EMER CONDITION. AN EMER WAS NOT DECLARED. #1 FLT ATTENDANT WAS QUICK TO BRING 2 WALKAROUND BOTTLES FOR US UP FRONT (NOT USED). ZNY CLRED US DIRECT TO MIA VIA HF. FO WAS ALSO VERY BUSY WITH DISPATCH WITH SITUATION; DIVERT; CREW LEGALITY; MAINT AND FUEL REQUIREMENTS; ETC. AFTER DOCKING AT GATE; MIA MAINT WAS ON THE ACFT RIGHT AWAY; FOUND THAT A PREVIOUS JUMPSEAT RIDER HAD IMPROPERLY STOWED A MASK; THAT AT SOME POINT INFLT BLED THE TANK DRY. TANK WAS REPLACED AND LEAK TESTED. HERE'S MORE: IRS DEV WAS EXTREMELY EXCESSIVE AT 56-80 MI OFF. SEEMS THE #3 IRS WENT S. MIA AVIONIC TECHNICIANS GOT ON THIS SIMULTANEOUSLY AND REPLACED THE COMPLETE GYRO PLATFORM.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.