If the plane is in the water SW of Perth, then it must have flown on autopilot, with both pilots dead or disabled and the cockpit locked, until it ran out of fuel.
How they got dead without the aircraft being destroyed is difficult to imagine, but an electrical fire that disabled ACARS and the transponder, and generated CO or some other toxic substance before burning out could do it.
Notice I did say, “IF the plane is in the water”. We should know that soon.
I don’t know about that. It has been said that with the changes in altitude (noted before in the news), there had to be some manual control for some part of the flight. To get that far out, they had to get back to cruising altitude for the most efficient flight (to fuel) before possibly running out of fuel (or some purposeful “ditching”).
Actually, I don’t think we will know soon. If your theory is correct (and I think its the most likely), then the plane flew at 40,000 feet until it ran out of fuel, and dropped nose first into the ocean. In that scenario, there’s not going to be any debris to find. Certainly nothing big enough to find in the southern Indian Ocean.
How would the fire have known when to go out, such as to leave the plane in the air until 0811+ Kuala Lumpur time?