Back to the basics...
I have noticed differing posting of the last 10 or so flight data points. The original postings in the early days of this event display the last 2 updates with a flight level of zero(0). The recent postings and news reports I've seen in the media seems to fill in those two values with the same 35,000ft as the rest of the 10 updates rather than the original reports of zero.
This maybe a key oversight. And why so many "experts" are focusing on other areas. I believe the last two reports of zero for altitude along with a constant reading for air speed may provide insight.
1. Is the SPEED input to the TRANSPONDER from a PITOT tube based system or another source, say GPS?
2. If it is PITOT tube based, does it share any sub-system component with the PITOT tube based system providing the ALTIMETER input to the transponder?
3. Once that is established a look at relative placement of the two pitot tubes, common power bus connections to the different/same modules, etc. could be analyzed.
4. Many failure possibilities for a perfectly functioning altimeter would produce erratic readings or at least none-zero reading. For an alt. that has ceased to work, the transponder or the system will fill in "zero's" in the data packet.
The fact that the transponder is instantaneously reporting zero while the a/c is 7 miles high in the sky is a key piece of information. The lack of radio reports while the transponder is still working would indicate an in-cabin event which precluded a radio report. Then over a three minute period the transponder ceases reports all together.
It looks like this geographical area is where transponder updates become sketchy as some historic tracks lose data up to a point just short of reaching the Vietnam coast.
All of this points to a rapidly deteriorating electrical system in the aircraft.
The oil rig observation is interesting. The observer is over 300 nm away but it is a dark, cloudless night. His observation of a burning plane would be down near the horizon. But his comment that, from his vantage point, he could percieve no lateral motion lends credibility to his report as we know the plane had just turned more in his direction, head on along with the indication that the event took place much further away than it appears.
If one of those US destroyers in the area is ASW equipped they should run their towed array sonar along 060 to 075 from LKP. The idea it was still in the air for 4 hrs lacks any published data... same as the "military radar" theory. Lets see some data.