I am surprised even a heavily loaded bus, even with max derate would have had trouble getting airborne on a nearly 4 km long downhill sloping runway.
(of course safety heights etc would not be met and it may waffle into the air - but it should still accelerate without dramas...)
True; after all, the guys managed to get the groundhog A 340-3 airborne taking off from the taxiway (heading 250) rather than runway 32 at Anchorage some years back. Some 7000 ft available, but they still made it, albeit after running the tires over a snow "berm" (?) at the end. Continued on to Taipei without further ado (10 hr plus flight, so can't have been too light on takeoff). I believe the augmenting Capt on the jumpseat was a training guy, but I could be wrong; would need to reread the report.
Gremlins will forever be standing by waiting to trap the unwary.