[FatherofFive]

At one briefing, according to this person, officials were told investigators are actively pursuing the notion that the plane was diverted "with the intention of using it later for another purpose."

This would make one heck of a suicide bomb.

[Col Frank Slade]

Logical speculation would indicate this was a hijacking. Transponders turned off, low altitude flying to avoid radar. Perhaps the hijackers got disoriented flying for hours over water in darkness and crashed before reaching intended target / destination.