An aircraft cabin is the section of an aircraft in which passengers travel. Most modern commercial aircraft are pressurized, as cruising altitudes are high enough such that the surrounding atmosphere is too thin for passengers and crew to breathe.
Cabin of a Boeing 737 (Economy class) with typical seating arrangement
The British Airways World Traveller Cabin
Aircraft cabin control system on board an Airbus A319
"Executive Class" cabin of Boeing 777-300ER operated by Biman
Cabin pressurization is a process in which conditioned air is pumped into the cabin of an aircraft or spacecraft in order to create a safe and comfortable environment for humans flying at high altitudes. For aircraft, this air is usually bled off from the gas turbine engines at the compressor stage, and for spacecraft, it is carried in high-pressure, often cryogenic, tanks. The air is cooled, humidified, and mixed with recirculated air by one or more environmental control systems before it is distributed to the cabin.
An airliner fuselage, such as this Boeing 737, forms an almost cylindrical pressure vessel
The pressurization controls on a Boeing 737-800
An empty bottle, sealed at 11,000 m (37,000 ft), is crushed on descent to sea level, compared with one in its original state.
Outflow and pressure relief valve on a Boeing 737-800
