Plain English Meaning

A system that keeps the inside of the cabin at a comfortable, lower-altitude air pressure while the airplane flies high up where the real outside air would be too thin to breathe properly.

Full Definition

An aircraft system that pumps and regulates conditioned air into a sealed cabin so that the pressure inside the cabin remains higher than the outside air pressure at altitude. This allows occupants to breathe comfortably and avoid the physiological effects of high altitude, even when the airplane is flying where the outside air is too thin to support normal human function.

Context Anchor

Encountered in training for pressurized airplanes, especially during preflight checks, climb, cruise, , and any cabin pressure warning or abnormal indication.