TRACK DEV IN FOREIGN AIRSPACE.

Narrative

WE HAD JUST CROSSED THE NORTH ATLANTIC WBOUND AND RECEIVED OUR DOMESTIC CLRNC. WE WERE CLRED NA190 ACROSS CANADA. COMPANY PROCS CALL FOR CHKING AND VERIFYING THE RTE IN OUR MANUALS ONCE WE RECEIVE OUR CLRNC. WE DID THIS; AND ALL POINTS CHKED ALONG THE LEGS PAGE OF THE FMC. LATER I HAD STEPPED TO THE BACK OF THE ACFT FOR A MOMENT. EVIDENTLY; WHILE I WAS GONE; THE ACTING FO MUST HAVE CHANGED THE RTE ON LEGS PAGE FROM YNA-CASTR-YRI TO YNA-YRI. WHETHER WE WERE CLRED DIRECT IN BTWN THESE 2 POINTS OR WHAT WAS NEVER FOUND OUT AND I AND THE CAPT FAILED TO CATCH THIS AS WE WENT ALONG. AROUND ABOUT THAT TIME; ONE OF THE FLT ATTENDANTS CAME TO THE COCKPIT AND INFORMED US THAT 2 OXYGEN MASKS HAD DROPPED DOWN BUT NOT ACTIVATED. BY NOW THE ACTING FO WAS BACK ON HIS BREAK; SO THE CAPT AND I WERE DEALING WITH THE OXYGEN PROB. WE LOOKED UP THE PROB IN THE OPERATING MANUAL AND DISCUSSIONS WITH THE FLT ATTENDANT KEPT US OCCUPIED ON THAT PROB. ONCE THINGS SETTLED DOWN SOME; I WAS WATCHING THE FLT PLAN AND NOTICED THAT CASTR WAS A WAYPOINT IN BTWN YNA AND YRI BUT DIDN'T SHOW AS SUCH ON OUR FMC. I THEN PUT CASTR INTO THE FMC TO FIND OUT THAT IT WAS VIRTUALLY ON A DIRECT RTE BTWN YNA/YRI. WE PASSED 11 MI S OR ABEAM CASTR. TORONTO CTR NEVER MENTIONED ANYTHING; SO WE ASSUMED THAT MAYBE WE WERE CLRED DIRECT BTWN THE 2 FIXES SOMETIME AGO; OR IT WAS SOMEHOW REMOVED FROM THE RTE IN THE FMC! OUR PREOCCUPATION WITH RE-COMPUTING FUEL; ETC; FOR THE OXYGEN PROB; GOING TO A LOWER ALT FOR OPERATIONAL REQUIREMENTS; AND THE FACT THAT CASTR WAS ONCE IN THE FMC; LED US TO BELIEVE EVERYTHING WAS OK. I FEEL THAT; WHEN WE ALTERNATE SEATS IN THE AUGMENTED CREW; IT IS VERY IMPORTANT TO UPDATE THE OTHERS ON ANYTHING THAT TOOK PLACE; SO IN CASE ANY OTHER DISTR (IE: OXYGEN PROB) ARISES; WE ARE BETTER PREPARED FOR THE SIT. THE FO WAS BRAND NEW IN INTL OPS; SO THAT MAY HAVE LED TO THE NON-BRIEFING; ETC; WHILE OTHERS WERE GONE.