Well I flew the Frankfurt to Los Angeles route which totaled 5476 nmi with full tanks. At the start,the FMC reported "insufficiant fuel" with the 767 running out of fuel well before LAX.But as the flight progressed, it slowly began to show enough fuel to make the trip. By the time I landed at LAX,the plane still had 43,300 pounds of fuel. I was flying with real time weather which when flying an East to West route usually puts the aircraft into headwinds. On this trip at FL380,the highest headwinds that I noted were 66 kts. I flew the trip in real time but did not monitor a good deal of the flight as I let it run overnight.  The plane did fly very well and I had no problem performing an autoland at LAX. There does seem to be an issue with the way the FMC is calculating fuel usage.