Where the hell is the plane?
A Boeing 777 doesn't just disappear with no warning and no trace. What the hell?
The experts are working the scenarios but nothing at the moment seems to make sense. The plane was last heard from three days ago at its cruising altitude of 35,000 feet. That's the safest part of any flight.
Midair Mechanical Malfunction
A catastrophic event that made the plane come apart, other than being REALLY unlikely, would have left a huge debris field which no one, at least so far, has been able to locate.
A mechanical failure which brought the plane down intact would have allowed time for a distress signal which apparently was never sent. But again, given the duplicate and triplicate systems of a 777, it's hard to imagine what sort of failure this could have been.
A Bomb or other Explosion
The same problems exist with this scenario as with a mechanical failure. Besides, no one has claimed responsibility and a plane carrying mostly Malaysian and Chinese passengers doesn't seem to be nearly as likely a target as a European or American aircraft.
Of course it might be an easier target and I suppose the motive could have been one where credit isn't an issue but there's still the problem of no debris and no distress call.
One possibility that has been suggested is a relatively small bomb that blew a hole in the aircraft that caused decompression but didn't destroy the flight integrity of the plane. The decompression could have knocked out passengers and crew but left the plane traveling on auto pilot only to eventually crash on land somewhere.
The problems with this are (1) why didn't even unreliable radar detect the aircraft and (2) why where there no automatic messages signaling distress and course?
That's not so easy any more these days. The cockpit door would have been locked and pilots have transponder codes they can enter to indicate a hijacking is occurring.
Besides, where the hell was the plane hijacked to? It didn't land anywhere that anyone is aware of.
Granted there are the two stolen passports that were used and some people claim that radar detection in that area isn't as reliable as in other airspace (but others disagree), but still, where's the plane?
Remember the Egyptian flight a few years ago that the co-pilot supposedly crashed into the Atlantic? Something like this could have occurred here but it's pure speculation. This is no evidence that anything of the sort occurred.
There is evidence that the plane started to turn as if to head back to Malaysia. This could mean there was a problem and the pilots had decided to turn back but things went to hell before they had a chance.
Still, see all the problems cited above with mechanical failures.