I wonder if any investigations were done on the finances of the crew, just to rule out foul play.
I'm sure they are checking all leads at this point. I think many of theories proposed in this thread, are very plausible. Well I say plausible. At least to me, all of this seems like a lot of effort. Like let's say they took the plane for ransom (kidnapping rich people on the plane). Taking an entire plane full of people, and making it disappear..just for a ransom? Sounds like a lot to do, just for that. Especially when they could have nabbed these people when they were on the ground.
Smuggling drugs, or weapons..and stealing a plane to get it to its destination? I guess a little more plausible, if the amount of weapons they had were worth a lot of money. It begs to question, how they got the drugs/weapons on the plane in the first place. But if its an inside job, maybe more doable.
If it was a terrorist attack, it seems like a lot of work, just to jack a plane (not crash it), and basically make it disappear. For what purpose? To use the plane at a later time? To smuggle themselves across the border?
I'm not really sure which one is the most plausible scenario. I mean, it seems like so much risk/ a lot of effort just to accomplish any of these goals.