AN ACR B767 FLC USED IMPROPER PROC TO ENTER THE RTE INTO THE FMC AND THEN THIS DATA WAS XCHKED IMPROPERLY. THE ACFT GOT OFF COURSE UNTIL THE ARTCC CTLR GAVE A NEW CLRNC DIRECT TO A WAYPOINT.

Narrative

EZEIZA CTR ASKED OUR HDG; THEN VECTORED US DIRECT PAGON. ORIGINAL CLRNC READ: UA300 GUA; UA301 PAGON; DIRECT VANAR; PAGON 1 SAEZ. WE THEN REALIZED THAT WE HAD BEEN TRACKING DIRECT EZE AFTER GUA INSTEAD OF UA301 PAGON. POS APPROX 10 NM NE PAGON; 4 NM E OF UA301 TRACK CTRLINE. 10 HRS OF ALL NIGHT FLYING HAD ELAPSED; ALL 3 PLTS WERE AT STATIONS IN COCKPIT. FMC HAD BEEN PROGRAMMED FOR UA301 PAGON; ARRS PAGE: PAGON 1A; ILS 11 ARSOT TRANSITION. ATIS ADVISED ILS RWY 35 IN USE. WHEN ILS RWY 35; EZE TRANSITION WAS SELECTED; THE STAR WAS OMITTED. WHEN IT WAS ACTIVATED NOT ONLY WAS PAGON 1A STAR ERASED; BUT ALSO UA301 PAGON; LEAVING EZE AS THE NEXT WAYPOINT AFTER GUA. WE IMMEDIATELY HEADED DIRECT PAGON AND WHEN IN CONTACT WITH EZEIZA APCH WERE VECTORED AND CLRED DIRECT EZE. IMPROPER PROCS WERE FOLLOWED IN THAT VERIFICATION OF THE NEW APCH SELECTION; ILS RWY 35; EZE TRANSITION; WAS NOT COMPLETED UNTIL AFTER ACTIVATION INSTEAD OF BEFORE EXECUTION. ALSO; THE DISCONTINUITY WHICH RESULTED WAS CLOSED WITHOUT VERIFICATION PRIOR TO EXECUTION. THUS; NONE OF US CAUGHT THE FACT THAT WE WERE TRACKING DIRECT EZE VERSUS DIRECT PAGON AND THAT THE FMC HAD DROPPED UA301 PAGON AND PAGON 1A STAR. OTHER CONTRIBUTING FACTORS: FATIGUE. WE WERE LULLED INTO ACCEPTING EZE AS THE NEXT WAYPOINT. IT MADE SENSE WHEN WE LOOKED AT THE HSI. THE APCH WAS NOT ILS RWY 35; EZE TRANSITION (VERSUS ILS RWY 11). BUT WE HAD NOT YET BEEN CLRED DIRECT EZE.