My dad was in the Air Force. There was no may day on Air France Flight 447 because of the rapid depressurization of the air plane. He said that at the normal cruising altitude of 32,000 ft, if the plane is depressurized you have about 2 to 3 seconds of consciousness before passing out. The air in your lungs, intestines, and sinuses are sucked out. If you have any air pockets in the fillings in your teeth, the fillings will pop out.
He said at that altitude the temperature is -58 below zero. It would take 5 minutes to free fall from 32,000 feet to 14,000 feet where you would not need an oxygen mask.