Which component is NOT part of an airplane's pressurization system?

The pitot tube is not part of an airplane's pressurization system. Instead, it serves a different purpose related to measuring airspeed and providing critical data for navigation and performance calculations. The pitot tube measures the dynamic pressure of the air, which helps determine how fast the aircraft is moving through the air, and is essential for the operation of the airspeed indicator.

In contrast, the other components listed are integral to the functioning of the pressurization system. The cabin pressure regulator controls the pressure within the cabin to keep it within a safe and comfortable range for passengers and crew. The source of air, typically provided by the engines or an auxiliary power unit, supplies the necessary air to maintain cabin pressure. The outflow valve regulates the amount of air that leaves the cabin, thus playing a crucial role in managing the pressure levels during flight.

Understanding the distinct functions of these components helps clarify why the pitot tube, while important for flight safety and performance, does not belong to the pressurization system.