Taupo:

from what i have read so far, i have heard to stories. One that the pilot entered the runway on the intersecting runway, so he has about 8500ft of runwway to work with. The other speculation, reported by an eye witness (a jetsgo pilot) said that the aircraft entered the runways on a taxi way approximetly 2000ft down the runway, leaving him with only about 6600ft of runway, which is under 747 certified operations minimums.

Either theory is plausable, the tower must have seen what happened as well. If he did have nearly the full length of the runway, the only reasons i can think of is that he under calculated V1,V2 VR speeds, and therefore assumed he would need less runway, so he used less power to save fuel, which is common practice. Similarly, i have read that the pilot may have only had 10 flaps on, and on a loaded 747 takeoff, 20 is required. This would mean that there would be less lift, and longer runway is needed, which even if the speed were calculated accurately could be one of the causes of lack of lift. I have a feeling it is going to boil down to an over weight aircraft, not correct speed calculations, and possible under use of flaps.

To look at the second theory of he used 6600 ft of runway, its very easy to see why a full 747 can not talk off from 6600 ft.