Some of the facts now known about the flight such as its transponder having been turned off, indications that the plane continued to fly at length at altitude afterwards and other satellite data indicating flight path have all contributed to the shift in focus.
One element reported was a curious profile in change of altitude with the plane climbing to its maximum operating ceiling above 50,000 feet above sea level and then returning to lower operating altitudes.
If equipment malfunction is ruled out, which apparently has been the case in the view of the investigating agencies, then what purpose would it serve hijackers to take the plane above 50,000 feet ?
Pilots are familiar with hypoxia - the loss of consciousness due to insufficient oxygen at altitude. Hypoxia is one of the dangers of operating aircraft above 14,000 ft. If oxygen isn't restored in time the condition becomes fatal.
The ability of a person to function with hypoxia for any length of time is related to the altitude and called Time of Useful Consciousness or TUC - at 35,000 useful consciousness is about 30 to 60 seconds - above 50,000 feet a person will become unconscious in 6 to 9 seconds !
Are the passengers and most of the crew already dead ?
Unfortunately, I can think of only one reason that hijackers would risk taking a plane above 50,000 feet while carrying several hundred passengers who could potentially interfere with a hijacking in progress - and that would be to immediately disable them.
