AN OCEANIC FLT FROM LAX TO KIX (ZOA AIRSPACE) STARTS OFF ON A WRONG TRACK DUE TO CONFUSION OF CLRNC RECEIVED. FLC HAD RECEIVED 2 PDC'S BUT NOT ENOUGH INFO ABOUT THE CLRNC WAS MADE BTWN THE 2 CLRNCS TO HELP FLC IDENT HOW THE PDC DIFFERED.

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THE DEP OF ACR BB; JUN/XX/97; LAX-KIX; WAS DELAYED DUE TO A MECHANICAL PROB WHICH RESULTED IN AN AIRPLANE CHANGE. ORIGINALLY SCHEDULED TO DEPART AT XA10Z; THE FLT EVENTUALLY DEPARTED LAX AT APPROX XC50Z. THE FLC WAS MADE UP OF THE CAPT; FO; AND 2 FO RELIEF PLTS. I WAS ONE OF THE RELIEF PLTS. DURING THE PREFLT PHASE IN THE REPLACEMENT ACFT; ACR DISPATCH ISSUED A SECOND FLT PLAN FOR THE FLT; 'RELEASE 2;' WHICH WAS DIFFERENT FROM THE ORIGINAL IN THE OCEANIC ROUTING; THOUGH THE INITIAL ROUTING AND FIRST SEVERAL FIXES WERE IDENTICAL. FLT PLAN #2 WAS LOADED INTO THE FMC AND PDC WAS RECEIVED FROM ATC VIA ACARS. THE PDC PRINTOUT NAMED THE FIRST FEW FIXES; THEN INDICATED 'AS FILED' AS IS NORMAL IN THE PDC FORMAT. THE FLT TOOK OFF AT XD03Z. AT APPROX XD35Z THE OTHER RELIEF PLT AND I LEFT THE COCKPIT TO BEGIN OUR REST PERIOD IN THE CREW REST QUARTERS. APPROX 1 1/2 HRS LATER; AS I PASSED THROUGH THE COCKPIT ON THE WAY TO THE LAV; THE CAPT TOLD ME THAT ON THEIR FIRST OCEANIC NON RADAR POS RPT; ATC HAD QUESTIONED THE RTE BEING FLOWN AS NOT WHAT ATC EXPECTED. APPARENTLY; ATC HAD EITHER NOT RECEIVED OUR DISPATCHER'S FILING OF 'FLT PLAN #2;' OR HAD FAILED TO ENTER THE CHANGE INTO THE ATC SYS. THE FLT WAS SUBSEQUENTLY CLRED ON OUR INTENDED ROUTING (#2); AND NO ACFT TFC CONFLICTS OR DEVS OCCURRED. UPON REFLECTION OF THIS OCCURRENCE; IN ADDITION TO THE ABOVE FAILURE; THE FORMAT OF THE PDC CONTRIBUTED TO THE ERROR BECAUSE IN ITS ABBREVIATED FORMAT THERE WAS A BUILT-IN AMBIGUITY THAT ALLOWED IT TO FIT EITHER FLT PLAN. 2 SUGGESTIONS TO REDUCE THE CHANCE OF A RECURRENCE OF THIS TYPE: 1) AMPLIFY THE FORMAT OF THE PDC SO THAT AT LEAST THE FIRST 1 OR 2 NON RADAR OCEANIC FIXES OF INTL FLTS PLANS BE PART OF THE INITIAL ROUTING TEXT. THIS WOULD BE AN ATC ADMINISTRATIVE CHANGE. 2) WHENEVER MORE THAN 1 FLT PLAN HAS BEEN ISSUED FOR A FLT; A FULL RTE READBACK OF THE ATC CLRNC SHOULD BE REQUESTED BY THE FLC; ESPECIALLY WHEN THE TEXT OF THE PDC WOULD FIT MORE THAN ONE OF THE FLT PLANS.