@finest... et al...
The oxygen problem we are seeing is different than a simple lack of oxygen. Even if it was and not contamination, then you would not hear a MayDay call. You would see a smoking hole.
It was the same thing with our gee-loc crashes in the Viper back in the early days. No call, as the dude was unconscious. We had video recorders of our HUD and we also had a recorder in the seat to grab the last minute or so of flight conditions if we ejected. In other words, you could not lie to the accident board.
I just have this feeling that the crew became incapacitated for one reason or another and couldn't eject.