Single point of failure
We spend a lot of time trying to eliminate single points of failure. We do this because many years of hard won and at times bitter experience have shown that single points of failure are weaknesses, and that redundancy intrinsically makes systems much less likely to fail.
When I fly in a helicopter, I sometimes think about the various single points of failure.
There is an enormous amount of redundancy built into modern airliners, and I applaud the efforts of engineers over the years.
There is still a major single point of failure. However unpleasant, we do need to consider this. Especially with several (widely accepted) precedents involving over recent years (and not counting 9/11 here).
Clearly we are all interested in this incident. To this discussion, we all bring our past experience, professional background, and personal biases and prejudices. A balanced discussion that attempts to integrate our differences and cancel out bias is most likely to lead to the answer.
I find some of the theories with 100's of posts a bit to hard too accept, and there is no single point of failure and too many things have to line up just right. We have some event which simultaneously destroyed all forms of communication and incapacitated the pilots, but left the autopilot fine. Or we have hypoxia (either sudden or gradual onset) which also knocked out the transponder. Or we have a fireball across the sky seen from a oil rig far away, but no debris you would expect to find at the end of such an event. While some things may be conceivably possible, that does not make them plausible.
As more information slowly comes out, these theories are starting to fall down.
Against this background, I can't help wondering why the few posters speculating about a single point of failure are repeatedly deleted.