Narrative:

Normal operations until 5 hours into flight.we operated in 'econ' which showed greater fuel and still an on time arrival; and very near flight planned M.84. We operated and climb near as the flight plan indicated; and we held steady at 200 to 400 pounds ahead on fuel; and 200 to 500 pounds under burn; again until 5 hours into flight.at crew change we first went to 600 pounds behind from 200 pounds ahead and to 600 pounds over burn from 300 pounds under burn. We received ATC clearance to cruise M.83 for the crossing as this was close to 'econ' and indicated about 1;200 pounds better fuel at landing. Tailwind had drop about 20 KTS from flight plan.fuel flows where averaging under the flight plan. The burn and fuel was noted to relief crew. Upon return from rest increased over burn was noted to me at 140W as 2;100 pounds and behind 2;000 pounds gross. Inflight highest over noted as 2;600 pounds if memory serves. We noted a 6;000 pounds over burn after landing; but I failed to check number carefully as we subtracted planned flight burn from the total burn (not the flight burn); the over burn was 1;386 pounds when subtracting the flight planned fuel burn from the actual flight burn; there was 2;900 pounds taxi out burn; and 2;000 pounds taxi in burn. We took off 5;000 pounds under flight plan weight; so I do find it strange that we burned extra fuel; we were able to save another 1;000 pounds as ATC cleared us direct to fix on the approach deleting the arrival and we did a constant descent saving that 1;000 pounds; which if added to the 1;386 pounds = 2;300 pounds very close to the highest over burn calculated in cruise near the end of the flight. There are good notes on the master flight plan to be utilized in the investigation. I have noticed that the burn and fuel does well and then starts slowly over burn about half way into flight; winds aloft and ground speed difference and temperature. Difference don't seem to explain this change half way into flight. We did request a reweigh of the cargo. Normal operation approach; landing; taxi in; shutdown and post flight.the crew and I wonder about cargo over weight; as there has been some cases of this in past; and perhaps fuel bias problems. Our error in calculating the over burn once on the ground was not helpful as well to the most accurate information; but I've corrected that calculation in the report and other will look at this as well. Continue to look into the cargo weight and fuel bias; thanks for your time and effort. I attached some pics of the master flight plan; not best quality; but may help in short term.

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Original NASA ASRS Text

Title: Boeing 777 Captain reported a discrepancy in the FMC fuel remaining estimate. Initially it showed they would be landing with extra fuel; then 5 hours into the flight it showed they would be landing with less fuel than planned. It may have been due to an un-forecasted wind shift.

Narrative: Normal operations until 5 hours into flight.We operated in 'econ' which showed greater fuel and still an on time arrival; and very near flight planned M.84. We operated and climb near as the flight plan indicated; and we held steady at 200 to 400 LBS ahead on fuel; and 200 to 500 LBS under burn; again until 5 hours into flight.At crew change we first went to 600 LBS behind from 200 LBS ahead and to 600 LBS over burn from 300 LBS under burn. We received ATC clearance to cruise M.83 for the crossing as this was close to 'econ' and indicated about 1;200 LBS better fuel at landing. Tailwind had drop about 20 KTS from flight plan.Fuel flows where averaging under the flight plan. The burn and fuel was noted to relief crew. Upon return from rest increased over burn was noted to me at 140W as 2;100 LBS and behind 2;000 LBS gross. Inflight highest over noted as 2;600 LBS if memory serves. We noted a 6;000 LBS over burn after landing; but I failed to check number carefully as we subtracted planned flight burn from the total burn (not the flight burn); the over burn was 1;386 LBS when subtracting the flight planned fuel burn from the actual flight burn; there was 2;900 LBS taxi out burn; and 2;000 LBS taxi in burn. We took off 5;000 LBS under flight plan weight; so I do find it strange that we burned extra fuel; we were able to save another 1;000 LBS as ATC cleared us direct to fix on the approach deleting the arrival and we did a constant descent saving that 1;000 LBS; which if added to the 1;386 LBS = 2;300 LBS very close to the highest over burn calculated in cruise near the end of the flight. There are good notes on the master flight plan to be utilized in the investigation. I have noticed that the burn and fuel does well and then starts slowly over burn about half way into flight; winds aloft and ground speed difference and temperature. Difference don't seem to explain this change half way into flight. We did request a reweigh of the cargo. Normal operation approach; landing; taxi in; shutdown and post flight.The crew and I wonder about cargo over weight; as there has been some cases of this in past; and perhaps fuel bias problems. Our error in calculating the over burn once on the ground was not helpful as well to the most accurate information; but I've corrected that calculation in the report and other will look at this as well. Continue to look into the cargo weight and fuel bias; thanks for your time and effort. I attached some pics of the master flight plan; not best quality; but may help in short term.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.