My bad, I meant theory du jour :):).
I agree, there was possibly a fight in the cockpit. I believe the reason for the ascent to 40,000 feet + was to kill the passengers and crew and possibly the co-pilot stepping out of the cockpit.
The pilot can dump the cabin pressure but the limit switches stop the dump at an effective elevation of 14,000 feet. There would be a leakage of about 1,000 - 1,500 feet per minute rendering everyone unconscious in about 6 minutes, dead in 10-15 minutes.
What about the drop down masks?