Narrative:

Just after passing frobay wbound; the controller asked us what we showed for our current and next waypoints. We told him; and were informed that those were different than what he had on his strip. He sent us to another waypoint a full degree south of where we were headed; then gave us a second and third waypoint; at which our 'new' route and our previous route should have merged. We entered the new points and linked up our route as advertised; and thought all was well. A few mins later; however; the controller suggested that we read off our entire route to ZZZ so he could verify that it all matched with his plan. It didn't. Almost every point on our flight plan from frobay to ZZZ was different. At that point we took a complete new routing/clearance from the controller and considered the situation sorted out. The more we thought about the disparity; the more concerned we became about what was going on; and we thought back to earlier in our flight. Had we been on our guard earlier; we'd have perked up when we got our oceanic clearance. The oceanic clearance was 'as filed' until the last 2 points. Our flight had been planned from n65w050 to n65w060 then kenki to coast in. Our oceanic clearance amended the plan to go from n65w050 to n64w060; then coast in at musva. Because of the increasing frequency of small route adjustments like this; it did not occur to any of the 3 of us that this coast-in change required any additional action on our part. We accepted the clearance; programmed the FMC; and considered it handled. A clue (that we didn't pick upon): our original plan had taken us from kenki to yfy. The oceanic changed the point after coast-in to yfb. They're almost co-located; so we thought nothing of it and hooked yfb to our original routing. It wasn't until we got the question from the controller that our issue became apparent. Upon reflection; we've realized the need to verify our entire domestic canadian routing upon first contact with the canadian controllers; which we didn't do. Things had gone too smoothly and had been too easy to manage for us to realize that we had a problem until the controller apparently saw us begin to diverge from his planned course on radar. Ramifications: thank goodness we coasted in under radar contact. Had we come in where we were originally filed; our incorrect flight plan would not have been discovered until our first position report inside yfb at which point we would have been more than 60 mi north of course (filed after yfy: n63w080-n62w090 -- cleared after yfb: n6030w090). New clearance continued with n58w100; yvc; J505 meeto; compr; stigs; J540 mlp. Flight planned route was very; very different. The only way we could have caught this flight plan error would have been to verify our entire route with ATC upon coasting-in. None of the 3 of us realized the need to do this. We do not routinely verify our domestic routings with canadian ATC. And we had a flight plan that seemed to work ok. Our new coast-in and subsequent fixes linked up nicely with our fpr. And; significantly; plotting would not have revealed this mix-up. A plot would have simply shown us on-course as flight planned and programmed in the FMC. I'm still not sure what happened here. It was as if there were 2 flight plans in operation: the one we had on board; and the one ATC was working from. There was a huge potential for a gross navigation error here; or much worse.

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Original NASA ASRS Text

Title: B777-200 FLT CREW WAS ISSUED AN OCEANIC CLRNC DIFFERENT FROM THE CLRNC FILED WITH ATC. THE FLT CREW ASSUMED THAT THE CLRNC THROUGH CANADIAN AIRSPACE WOULD REMAIN AS FILED; BUT DISCOVERED FROM CANADIAN ATC THAT THIS ROUTING HAD ALSO SIGNIFICANTLY CHANGED.

Narrative: JUST AFTER PASSING FROBAY WBOUND; THE CTLR ASKED US WHAT WE SHOWED FOR OUR CURRENT AND NEXT WAYPOINTS. WE TOLD HIM; AND WERE INFORMED THAT THOSE WERE DIFFERENT THAN WHAT HE HAD ON HIS STRIP. HE SENT US TO ANOTHER WAYPOINT A FULL DEG S OF WHERE WE WERE HEADED; THEN GAVE US A SECOND AND THIRD WAYPOINT; AT WHICH OUR 'NEW' RTE AND OUR PREVIOUS RTE SHOULD HAVE MERGED. WE ENTERED THE NEW POINTS AND LINKED UP OUR RTE AS ADVERTISED; AND THOUGHT ALL WAS WELL. A FEW MINS LATER; HOWEVER; THE CTLR SUGGESTED THAT WE READ OFF OUR ENTIRE RTE TO ZZZ SO HE COULD VERIFY THAT IT ALL MATCHED WITH HIS PLAN. IT DIDN'T. ALMOST EVERY POINT ON OUR FLT PLAN FROM FROBAY TO ZZZ WAS DIFFERENT. AT THAT POINT WE TOOK A COMPLETE NEW ROUTING/CLRNC FROM THE CTLR AND CONSIDERED THE SITUATION SORTED OUT. THE MORE WE THOUGHT ABOUT THE DISPARITY; THE MORE CONCERNED WE BECAME ABOUT WHAT WAS GOING ON; AND WE THOUGHT BACK TO EARLIER IN OUR FLT. HAD WE BEEN ON OUR GUARD EARLIER; WE'D HAVE PERKED UP WHEN WE GOT OUR OCEANIC CLRNC. THE OCEANIC CLRNC WAS 'AS FILED' UNTIL THE LAST 2 POINTS. OUR FLT HAD BEEN PLANNED FROM N65W050 TO N65W060 THEN KENKI TO COAST IN. OUR OCEANIC CLRNC AMENDED THE PLAN TO GO FROM N65W050 TO N64W060; THEN COAST IN AT MUSVA. BECAUSE OF THE INCREASING FREQUENCY OF SMALL RTE ADJUSTMENTS LIKE THIS; IT DID NOT OCCUR TO ANY OF THE 3 OF US THAT THIS COAST-IN CHANGE REQUIRED ANY ADDITIONAL ACTION ON OUR PART. WE ACCEPTED THE CLRNC; PROGRAMMED THE FMC; AND CONSIDERED IT HANDLED. A CLUE (THAT WE DIDN'T PICK UPON): OUR ORIGINAL PLAN HAD TAKEN US FROM KENKI TO YFY. THE OCEANIC CHANGED THE POINT AFTER COAST-IN TO YFB. THEY'RE ALMOST CO-LOCATED; SO WE THOUGHT NOTHING OF IT AND HOOKED YFB TO OUR ORIGINAL ROUTING. IT WASN'T UNTIL WE GOT THE QUESTION FROM THE CTLR THAT OUR ISSUE BECAME APPARENT. UPON REFLECTION; WE'VE REALIZED THE NEED TO VERIFY OUR ENTIRE DOMESTIC CANADIAN ROUTING UPON FIRST CONTACT WITH THE CANADIAN CTLRS; WHICH WE DIDN'T DO. THINGS HAD GONE TOO SMOOTHLY AND HAD BEEN TOO EASY TO MANAGE FOR US TO REALIZE THAT WE HAD A PROB UNTIL THE CTLR APPARENTLY SAW US BEGIN TO DIVERGE FROM HIS PLANNED COURSE ON RADAR. RAMIFICATIONS: THANK GOODNESS WE COASTED IN UNDER RADAR CONTACT. HAD WE COME IN WHERE WE WERE ORIGINALLY FILED; OUR INCORRECT FLT PLAN WOULD NOT HAVE BEEN DISCOVERED UNTIL OUR FIRST POS RPT INSIDE YFB AT WHICH POINT WE WOULD HAVE BEEN MORE THAN 60 MI N OF COURSE (FILED AFTER YFY: N63W080-N62W090 -- CLRED AFTER YFB: N6030W090). NEW CLRNC CONTINUED WITH N58W100; YVC; J505 MEETO; COMPR; STIGS; J540 MLP. FLT PLANNED RTE WAS VERY; VERY DIFFERENT. THE ONLY WAY WE COULD HAVE CAUGHT THIS FLT PLAN ERROR WOULD HAVE BEEN TO VERIFY OUR ENTIRE RTE WITH ATC UPON COASTING-IN. NONE OF THE 3 OF US REALIZED THE NEED TO DO THIS. WE DO NOT ROUTINELY VERIFY OUR DOMESTIC ROUTINGS WITH CANADIAN ATC. AND WE HAD A FLT PLAN THAT SEEMED TO WORK OK. OUR NEW COAST-IN AND SUBSEQUENT FIXES LINKED UP NICELY WITH OUR FPR. AND; SIGNIFICANTLY; PLOTTING WOULD NOT HAVE REVEALED THIS MIX-UP. A PLOT WOULD HAVE SIMPLY SHOWN US ON-COURSE AS FLT PLANNED AND PROGRAMMED IN THE FMC. I'M STILL NOT SURE WHAT HAPPENED HERE. IT WAS AS IF THERE WERE 2 FLT PLANS IN OP: THE ONE WE HAD ON BOARD; AND THE ONE ATC WAS WORKING FROM. THERE WAS A HUGE POTENTIAL FOR A GROSS NAV ERROR HERE; OR MUCH WORSE.

Data retrieved from NASA's ASRS site as of May 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.