This whole situation still continues to fascinate me, and by a process of elimination I reckon I’ve figured out what has happened.
I think it is safe to assume the plane was hijacked, or deliberately flown off course by one or both of the pilots. It does not seem credible to me that the plane suffered a malfunction or some sort and the pilots were unable to get a message out of some sort, if indeed they kept flying for several hours after radar contact was lost.
I think it is reasonably safe to assume the plane did not crash in the Gulf of Thailand, Malacca Straits, or the Andaman Sea. These areas are chock-full of shipping, fishermen, and other craft and debris would have been spotted by now, and somebody would have seen or heard something.
I think it is also fairly safe to assume that nobody pinches a plane full of passengers for the purposes of disappearing quietly. Precedent suggests that plane hijackings are quickly followed by political demands or spectacular collisions with iconic buildings. The lack of either occurrence suggests the first part of the plan was carried out, but not the second. I don’t buy the argument that the plane was hijacked in order to be used later: there are several ways to obtain a 777 without raising an international plane-hunt involving 239 missing people; if you want a flying bomb, a cargo plane would do just as well.
Therefore I think the most likely scenario is one whereby a pilot, or both pilots, carried out instructions to divert from their normal course before losing their nerve; or being overpowered by the other pilot, in the event only one was in on it. Or somebody else – either passengers, stowaways, or a combination of both – took over the plane and either lost their nerve or were overpowered. If the people in control of the plane were overpowered after a struggle, then the plane would have come down wherever it happened to be at the time. But if somebody lost their nerve, or found the second part of the mission could not be completed for whatever reason, I can envisage a scenario whereby those in control fly the plane as far out into the deep ocean as they can before the fuel runs out, thus minimising the likelihood of wreckage and the black boxes being found. This course of action would serve two purposes: it would save the faces of those who have lost their nerve (I can’t imagine al-Qa’eda gives second chances to operatives who have bottled out); and also destroy as much evidence as possible thus helping to protect the rest of the network back in Malaysia and elsewhere who organised it. The US might have congressional debates on whether water-boarding constitutes torture and a media which frets over the mishandling of a Koran, but I expect anyone who fell into the hands of the Chinese investigating team would be singing like a canary in pretty short order.
I therefore expect that the plane has come down miles into the Indian ocean somewhere, well out of sight of land or shipping, and at some point in the future bits and pieces will wash ashore or come up in a fishing net, which will lead to the black boxes being eventually found. The only thing I cannot for the life of me work out is what cause is advanced by somebody hijacking a Malaysian plane filled mostly with Chinese citizens. It’s that question which has me stumped over and above any other.