If it was a hijack scenario, then SinisterSal's scenario would make perfect sense, imo. Turn as the hijackers command, but also put another 'final' destination in, obviously the 'wrong' place, knowing that they would likely all be doomed anyway but that it being 'found' in the sea on the way to the South Pole would let the world know that something had gone desperately wrong as the pilots would never clearheadedly have programmed in such a destination.
Trouble is that could fit hypoxia too?
I do think the Malaysian Government is way way out of its depth. I think there will be all sorts of covert and overt pressures from the superpowers potentially involved too and I have no doubt the US would withhold information from Malaysia if it deemed necessary, and Russia and China too. It actually needs an independent organisation to look into this .
I also think that, in addition to individual countries prestige and resources there is the possibility that vested interests may have a part to play. Pulling all 777's across the world of that age and model would be hugely expensive, wouldn't it?. One would hope that that wouldn't be a factor, but there are plenty of examples of manufacturers (cars, baby buggies etc) 'only' pulling / adapting certain models after months/years of customer complaint / accidents? I am sure that Goldie might be able to reassure me on that point, so it might not be relevant - hope not!
I cant imagine those poor souls are still alive so I hope they find wreckage so at least the families have closure on that aspect.