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.
Military aircraft routinely fly in the 30,000 to 45,000-foot altitude range, thus, cabin altitudes will frequently be between 8,000 feet (565 mmHg pressure) to 16,000 feet (412 mmHg pressure).
In commercial air travel, particularly in airliners, cabins may be divided into several parts. These can include travel class sections in medium and large aircraft, areas for flight attendants, the galley, and storage for in-flight service. Seats are mostly arranged in rows and aisles. The higher the travel class, the more space is provided. Cabins of the different travel classes are often divided by curtains, sometimes called class dividers. Passengers are not usually allowed to visit higher travel class cabins in commercial flights.
Some aircraft cabins contain passenger entertainment systems. Short and medium haul cabins tend to have no or shared screens whereas long and ultra-long-haul flights often contain personal screens.