ACR LGT USED WRONG FUEL BURN WHEN COMPUTING FLT PLAN ANALYSIS. ACFT LANDED 600 POUNDS OVER MAXIMUM CERTIFIED LNDG GROSS WEIGHT.

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MY EMPLOYER RECENTLY STARTED THEIR OWN COMPUTERIZED FLT PLAN. OUR TKOF WT WAS APPROX 167000# AT PIT; PA. MAX LNDG WT OF OUR ACFT; 154500#. FAA INSPECTOR ON JUMPSEAT; CHK AIRMAN (ME) IN RIGHT SEAT CONDUCTING IOE FOR NEW UPGRADE CAPT IN LEFT SEAT. WE LANDED AT BOS 155100#; 600 LBS OVERWEIGHT. WE KNEW WE WERE OVERWT. CHKED OUR W/B THROUGH COMPANY RADIO. ALL WAS CORRECT; WE WERE 600 LBS HEAVY. NEW CAPT DISCUSSED POSSIBLE ALTERNATIVES AND AFTER CHKING OUR MANUAL; WHICH PROVIDES FOR OVERWT LNDGS; DECIDED RATHER THAN DUMP OR WASTE FUEL; WE WOULD LAND; ALERT BOS MAINT AND MAKE THE PROPER LOGBOOK ENTRY; WHICH WE DID. A NORMAL APCH AND LNDG FOLLOWED. THE FAA INSPECTOR'S OPINION WAS WE SHOULD HAVE BURNED THE FUEL DOWN RATHER THAN LAND. I DISCUSSED WITH HIM OUR MANUAL PROVIDES FOR OVERWT LNDG AND IT WAS CAPT'S DISCRETION. THE PROB IS COMPANY SHOWS AND USES FUEL BURN BASED ON BLOCK TO BLOCK TIME; IN THIS CASE 1 HR; 38 MINS BURN. OUR ACTUAL BLOCK-BLOCK TIME WAS 1 HR; 25 MINS WITH A TOTAL AIR TIME OF 1 HR; 6 MINS. ALSO; DUE TO NOT MUCH TFC (ATC) WE BEAT THE SHEDULED BURN BY 300 LBS. I HAVE TALKED TO OTHERS IN THE COMPANY RE THIS AND IT IS UNDER STUDY AT THIS TIME. IF COMPANY WT AND BALANCE WAS BASED ON A REALISTIC BURN; IN THIS CASE THE CREW WOULD NOT HAVE BEEN SET UP. I CAN DEFEND THE NEW CAPT'S ACTION AS CAPT'S DISCRETION AND ENTIRELY LEGAL. HOWEVER; PERHAPS UNDER THE CIRCUMSTANCES A MORE CONSERVATIVE APCH WOULD HAVE BEEN BETTER. I THINK THE ISSUE WILL BE DROPPED BY OUR LCL FAA. WE'LL SEE.