CORP JET MISPROGRAMS FLT COMPUTER FLIES 150 MI OFF COURSE.

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WE DEPARTED THE BERMUDA CTL AREA IN RTE TO FLANN INTXN. WE HAD GIVEN ESTIMATES TO FLANN BASED UPON OUR NAV EQUIP (DUAL IRS; OMEGA; DME) AND THE FLT PLAN. ALL FIXES HAD BEEN LOADED INTO OUR NAV COMPUTER BY MYSELF; BUT HAD NOT BEEN XCHKED BY THE OTHER PLT. WE CROSSED THE FIRST FIX ON TIME AND COURSE; THE ACFT AUTOMATICALLY SELECTED THE NEXT FIX (FLANN) AND PROCEEDED TO TRACK TO IT. OUR FLT PLAN CAME FROM COMMERCIAL WX SVC IN STANDARD FORMAT. ABOUT 35 MIN INTO THE NEXT LEG OF THE FLT PLAN THE OTHER PLT COMMENTED TAG ACFT NEEDED TO PROCEED QUITE A WAYS NE ON THIS FLT PLAN. AT THAT MOMENT I LOOKED CLOSELY AT OUR COURSE AND NOTED IT SEEMED CONSIDERABLY DIFFERENT THAN THE CHART. I HAD NOT CONSULTED THE CHART PREVIOUSLY; ONLY THE TIME AND FUEL ON THE FLT PLAN. LOOKING CLOSER AT THE CHART NOW; AND OUR ACTUAL LAT-LONG I DISCOVERED WE WERE 130 NM E OF FLANN INTXN. AT THIS TIME WE CALLED COMMERCIAL RADIO ON HF AND TOLD THEM OF THE ERROR. ATC CONTACTED US; CHKED FOR TFC; THEN ISSUED US A NEW ROUTING AND DIRECT FLANN THEN AS FILED (BERMUDA-SLC). GOING BACK NOW AND CHKING THE FLT COMPUTER I FOUND THAT I ENTERED THE LONGITUDE OF FLANN THE SAME AS THE PREVIOUS FIX. THE PREVIOUS FIX LAT/LONG ARE JUST ABOVE THE FOLLOWING ON THE FLT PLANS. HAD WE XCHKED EACH OTHER WE WOULD HAVE FOUND THIS ERROR. WE WERE JUST COMING OFF A 2 WK EUROPE TRIP; AND HAD SPENT A LONG DAY IN THE ACFT THE PREVIOUS DAY. I CAN ONLY ATTRIBUTE THIS ERROR TO COMPLACENCY IN THE COCKPIT; PARTIALLY DUE TO AN EXTREMELY ACTIVE FLT SCHEDULE. WE HAD BEEN TO EUROPE 3 TIMES IN 2 1/2 MONTHS PLUS OTHER DOMESTIC FLYING. THERE ARE ONLY 2 OF US IN THE FLT DEPT; AND WE BECOME COMFORTABLE WITH EACH OTHER. IN RETROSPECT ANY OCEAN XING SHOULD BE TREATED THE SAME. WE CANNOT TOLERATE COMPLACENCY IN THE COCKPIT. SUPPLEMENTAL INFO FROM DUPLICATE ACN 205168. WE NEGLECTED TO LOAD EACH COMPUTER INDIVIDUALLY; WHICH WOULD HAVE ASSISTED US IN CATCHING THE ERROR.