Fuel Burn ?

[biggles70]

Last night I flew from YBBN to YBCS, during the flight I noted the Fuel burn figures at different stages of flight.
On landing I used the figures I obtained to plan a LONG flight. (6hrs) By my calculations I should've just had enough fuel for the flight.
After flying the takeoff and climb I watched for about 20 mins into the cruise and then recalculated the fuel figures. The FMC indicated Id have 1.4T remaining at destination. Everything looked OK. I then went to bed leaving the plane to fly on. Id set my alarm to wake me about an hour before TOD. After a hit of the snozze button or two I finally got up to find that Id just run out of fuel. The panel was dark and I was in a gentle glide. Cheating, I added more fuel and restarted the engines and continued to my destination.
I hadnt encountered any headwinds (no live weather to derive them from) so now Im puzzled as to why I ran out. It would appear that the actuall burn in FS is a bit higher than what we see on the FF gauge.

Any thoughts on this?
Next time Ill stay awake.

[biggles70]

ummmmmmm...

Call me stupid.
For some reason, the fact that someone had made a Fuel Planner for the 737, and that Id downloaded it, had escaped me.

Ive just put the appropriate figures into the Fuel planner and guess what, I didnt have enough fuel (duhhh. I knew that after the engines stopped). The flight is certainly possible, but not at the weights I had planned. Back to NAV school for me on flight planning. Im shocked I got it so wrong.

Biggles70