electrical fire, plenty of time for a mayday signal. there are protocols that are followed, none were, almost the exact opposite was done.
SARS pinged for 7 hours, establishing the 1000 mile radius of flight path possibilities.
You may know airplanes and electronics, but we are also dealing with people and probabilities. The simplest possibility is the most likely. The simplest explanation with the highest probability of being correct is some kind of failure and crash. The rest its just filler and hype. All terrorist scenarios are complicated, unlikely, and with no understandable goal or outcome. Stealing a plane scenarios are just as hare-brained. But then you are reading fox news.