What is the cabin of an aircraft?

The cockpit, or flight deck, is the piloting station located at the front of the aircraft, where two pilots —captain and first officer on most current commercial jets— operate the flight controls, avionics and communications with air traffic control. From there the trajectory, speed, engine settings and all aircraft systems are controlled, supported by electronic displays that in the most modern models replace most of the analog instruments of earlier generations. In Spanish the word "cabina" alone is sometimes used for the cockpit and sometimes for the rest of the aircraft, which creates confusion; in English this ambiguity doesn't exist because "cockpit" and "cabin" have been distinct words from the start.

The passenger cabin is the pressurized compartment where passengers travel, usually divided into several service classes with different seat densities, and separated from the cargo holds beneath the floor. Since the September 11, 2001 attacks, the door separating the two cabins has been reinforced, stays locked throughout the flight and can only be opened from inside or with an access code controlled by the flight crew, a security measure that completely changed the design of this access point across all commercial aviation after that date. The pressurization of both spaces works as a single system that regulates the pressure difference with the outside as the aircraft gains altitude, so that at cruising altitude, around 11,000 meters, the interior feels equivalent to a low-altitude valley rather than a mountain summit.