evanplus - Not been around here for about 5 days so 'm sorry if this has already been asked.
Has the projected range charts for this flight been calculated at maximum operating heights/speeds? I noticed the press were saying the aircraft could have decended to as low as 5/6000ft to avoid radar but this would have had a drastic effect on fuel consumption surely.
Most, if not all, of the experts have done a poor job of explaining this. If you're operating the aircraft efficiently your fuel flow actually decreases at low altitude(3%, 250kt vs. .84) so your endurance goes up slightly.
The big hit is on your range. Range is cut drastically at lower altitude.
Flying at optimum cruise altitude increases your fuel flow by approx. 3% but your speed increases resulting in a range increase of over 70%.
So endurance is fairly constant while range changes significantly.