AIR CARRIER MLG EXECUTES A DIVERSION TO ALT ARPT AFTER DISCOVERING THAT FUEL REMAINING WAS INADEQUATE FOR REMAINDER OF TRIP.

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AIRLINE FLT OF MAY/XX/92 WAS SCHEDULED FROM CHICAGO TO TORONTO. NORMAL FUEL CHKS WERE MADE COMPARING FLT PLAN RELEASE FIGURES WITH THOSE ON TKOF PERFORMANCE DOCUMENTS. CHKS OF RESERVE; ALTERNATE; AND HOLDING FIGURES WERE ALSO MADE. OVERLOOKED; HOWEVER; WAS A XCHK I NORMALLY MAKE TO COMPARE FLT TIME WITH SCHEDULED BURN. I ALSO DID NOT NOTE THAT THE TOTAL FUEL FIGURE WAS LOW FOR A FLT OF THIS NATURE. AFTER DEP; I WAS BUSY WITH A COM AND DID NOT SEND FOR THE ACARS FLT PLAN; WHICH GIVES TARGET TIMES AND FUEL OVER FLT PLAN POINTS; UNTIL WELL PAST KEELER. SOON AFTER; THE FLT WAS CLRED DIRECT TO SALEM; THEN GIVEN A HDG FOR LONDON; ON. JUST PAST SALEM; A FUEL CHK WAS MADE AND THE FO AND I DETERMINED THAT WE WERE APPROX 3000 POUNDS OF FUEL SHORT OF WHAT WOULD HAVE BEEN NECESSARY TO CONTINUE TO TORONTO. A QUICK CHK OF THE FUEL GAUGES WAS MADE TO DETERMINE THAT WE WERE PROBABLY NOT LOSING FUEL. WE CHKED THE FLT PLAN RELEASE AND DISCOVERED THAT THE BURN OFF THE 1 HR SEGMENT WHICH SHOULD HAVE BEEN ROUGHLY 7000 POUNDS; HAD BEEN PLANNED AT 2683 POUNDS. 90 MI E OF LONDON; I COORD WITH DISPATCH AND ATC FOR A DETROIT LNDG. THE ACFT LANDED WITH 3900 POUNDS OF FUEL ON BOARD. I CALLED DISPATCH FROM DTW. HE HAD DISCOVERED THAT THE BURN RATES FOR OUR PARTICULAR ACFT WERE BEING ADJUSTED; WHICH HAD SOMEHOW CONTRIBUTED TO THE COMPUTER FLT PLAN ERROR. IT IS AN UNDERSTATEMENT TO SAY THAT THIS OCCURRENCE HAS SERVED TO RE-EMPHASIZE THE NECESSITY OF CAREFUL CHKING OF FLT PLAN FUEL. SUPPLEMENTAL INFO FROM ACN 210937: AFTER LEVELING OFF AT OUR CRUISING ALT I NOTICED THAT THE FUEL BURN WAS 3000 POUNDS MORE THAN FLT PLAN BURN. I INFORMED THE CAPT IMMEDIATELY. AFTER CLOSER EXAMINATION OF THE COMPUTERIZED FLT PLAN; IT BECAME OBVIOUS THAT THE COMPUTERIZED FLT PLAN WAS IN ERROR. DISPATCH; THE FO; AND CAPT SHOULD HAVE NOTICED THE MISTAKE ON THE FLT PLAN. HAVING NEVER EXPERIENCED A PROBLEM WITH A FLT PLAN; COMPLACENCY WAS A FACTOR EVEN THOUGH ON PAPER NOTHING WAS WRONG. COMMON SENSE SHOULD HAVE PREVAILED.