At long last, a plausible scenario of what happened to Flight 370 has emerged. By plausible I mean that the scenario fits all the known facts.

The key piece of evidence has finally been released by Malaysian authorities: Pilot Spoke to Air Controllers After Shutoff of Data System (NYT.com).

This proves that one of the pilots turned off the ACARS communications link and then reported to air traffic control (ATC) as if all was normal. Twelve minutes later, one of the pilots switched off the aircraft's transponder, which transmits the aircraft's altitude and location.

This sequence of events more or less proves that one of the pilots was in charge of the aircraft. Given the lack of evidence of duress, this sequence strongly suggests one of the pilots was executing a plan of his own rather than following orders of hijackers.