I read a report earlier that said there were only two 30-minute engine data transmissions - around take off and approaching cruising altitude.
That is exactly what Malaysian Airways has reported - there were two and only two data transmissions that they knew about - takeoff and cruise. They know of no others - the speculation is contagious.
Those engines don't transmit continuously - they transmit at significant events or every 30 minutes.
Not sure if there's a way to turn that off from the cockpit. If there is, then the hijacking theory still has legs.
If not, then there's no way to fly for 4+ more hours without that data being transmitted, and no reason (that I can see) for RR or Boeing or Malaysian Airways to cover it up.
that means nosedive or massive explosion.