Ok, not an expert, but if they saw it drop 600 feet and then nothing would that be indicitive of a massive airframe failure? Meaning disintegration.
Sounds like you are making a good educated guess.
It would be helpful if someone else who watched Fox could confirm this is what they said. Anyone? And that is that they said the plane dropped 600 ft. and then vanished.
This seems to be the most important piece of information so far and otherwise, we practically have nothing and I’m reading some of the news reports as well.