On a jet airliner at over 30 thousand feet the air has too little oxygen for me to breathe therefore on a long haul flight with 300 other people how can we survive for 12 hours?

Answer 1

Passengers and crew survive because the aircraft cabin is pressurized to a lower altitude level. If I recall correctly, the pressure level is usually 6 to 8 thousand feet.

On most airplanes, compressed air is bled off the engines (before the air reaches the combustion chamber inside the engine) and is ducted to the air conditioning system. There most of it is cooled (and hot air is mixed with it to control the temperature inside the airplane--it can be 50 degrees below zero at 30,000 ft) and (usually) some recirculated air from the cabin (which has been run through filters) is also mixed with the incoming air. This is then ducted into the cabin, through an overhead air distribution duct and those little 'eyeball' vents above your seat. The airplane is sealed to a great extent; there are some leaks that are allowed, but mostly the cabin pressure is controlled automatically by use of an outflow valve (or valves), which allows some air to leave the airplane and keeps the cabin pressure to safe levels. There is also a separate safety valve that opens in case the main outflow valve(s) fails and the cabin pressure gets too high. There are of course variations from one airplane design to another, but this covers the basics. == The percentage of Oxygen in the air is the same at the ground as at high altitude(as far as I know). But at altitude the air is thinner so the amount of air you can breathe in is less. So the less air you can breathe, the less oxygen you can get. As the airplane pressurizes the air, it compresses it back to the density that it would be for 8,000 feet. The airplane does not add oxygen or create oxygen except in emergency conditions when the airplane becomes depressurized and the O2 masks drop out. The above answer is correct. The reason airliners have such small windows despite their large size is because larger windows would have to be excessively heavy to withstand the pressure. A cabin pressure blowout at high altitude would be a disaster for everyone on the plane. The movie scenes of people being sucked/blown out of the plane are not just dramatizations. It has happened more than once in the past.