How Cabin Pressurization Keeps You Alive At 40,000 Feet

Modern aircraft are designed to fly at high altitudes of between 28,000 and 35,000 feet. This is because aircraft consume less fuel and fly in relatively smooth air, avoiding bad weather and turbulence. However, the human body is not designed to survive at such high altitudes, so the air pressure inside the cabin has to be controlled. At 40,000 feet, the outside air is so thin and has only a fraction of the oxygen available in comparison to at sea level. An unprotected person would lose useful consciousness in well under a minute.