The highest altitude is 8,000 ft. But depending on the aircraft, it is usually pressurized to around 6,500 to 7,000 ft.
Airplanes often fly at great altitudes, of 10 kilometers or more. People would have serious trouble breathing at that altitude.
Generally yes. Few large commercial airplanes travel under 10,000 feet where you need oxygen or pressurization.
Most airplanes fly at high altitude because it is faster and safer as long as the cabin is pressurized. There is less clouds and turbulence. The airplane uses less fuel.
At 35,000 feet, a human would suffer severe oxygen starvation without a pressurized cabin. Also known as "death". A pressurized cabin in a commercial - or military - airliner is essential at high altitude.
Airplanes are pressurized because the air is very thin at the altitude that the plane flies. The average passenger jet has an altitude of about 30,000 to 40,000 feet. At this altitude, humans can’t breathe very well and our brain gets less oxygen. This is called hypoxia and can cause slower thinking, dimmed vision, and death. Airplane pressurization is necessary for the survival of the passengers on board.
Airplanes need to be pressurized because the atmospheric pressure, at such a high altitude, acts upon your body. Your body is trying to adjust to maintain equal pressure, causing your ears pop. Because your body cannot maintain equal pressure by itself, the airplane makes up for the rest of the pressure that is needed to equalize the atmospheric pressure.
Because the cabin inside the plane is pressurized?
They would suffocate.
Boeing Commercial Airplanes was created in 1916.
Boeing Commercial Airplanes's population is 60,000.
The majority are limited to 10,000 or 12,000 feet (the height where you must use oxygen and/or a pressurized cabin). That's not a law, and some people own aircraft that operate on the same rules as commercial airliners.
Airplanes travel faster at higher altitude. But pilots don't travel better at high altitude. Above 10,500 feet, people start to be affected by oxygen deprivation: tunnel vision, slower reflexes, slower reaction times, impaired judgement, etc. Aircraft are pressurized so people don't fall asleep and/or die at high altitude. At regular commercial airline altitudes between 10,000 and 40,000', all aircraft have to have pressurized cabins. Pilots wear oxygen masks (with the gas turned off) at those altitude in case there is a pressurization failure or a rapid cabin decompression. If one should eventuate, they already have on the mask, and all they have to do is turn on the oxygen.