Out of all the above dozens of posts only Les Paul has mentioned the obvious possibility that the a/c has been hijacked by one or both of the crew.
Latest news from ABC says that hijacking is now the dominant theory and at the time of the Malaysian Prime Minister's address saying this, police were searching the home of the captain of the aircraft.
Might be just another incorrect theory, but it would explain everything known so far and is probably more likely than the assumption that some passenger has taken over the aircraft.
