In very basic terms, how is the aircraft pressurized?

• A. Air is pumped into the cabin and the outflow valve regulates how much leaks out to control pressurization through an electrically controlled Outflow Valve (OFV)
• B. Pressurization is achieved by a fixed air volume in the cabin
• C. Cabin is pressurized by external air only
• D. Pressurization is controlled by manual venting

Answer: (A)

Pressurization is a continuous control process: conditioned air is added to the cabin, while a controlled vent lets air escape to outside. The system uses an air source from the engines and/or packs to push air into the cabin, and the outflow valve, which is electronically controlled, regulates how much air leaks out. By adjusting this valve, the cabin pressure is kept at the desired level as you climb or descend.

This approach is why the correct choice is best: it describes a active supply plus regulated exhaust to maintain pressure. It isn’t about a fixed volume, it doesn’t rely on external air alone, and it isn’t done manually—all those would fail to maintain a stable cabin pressure automatically.