If a cabin altitude warning occurs while cruising at high altitude, what is the first action in the approved procedure?

• A. Initiate rapid descent to a safe altitude.
• B. Immediately declare an emergency and land at the nearest airport without descent.
• C. Continue cruising and troubleshoot while maintaining altitude.
• D. Pull the circuit breakers to shut off the cabin pressure system.

Answer: (A)

When a cabin altitude warning sounds at cruise altitude, the immediate priority is to lower the cabin altitude by descending rapidly to a safe level. This action directly addresses the risk of hypoxia: at high altitude, the air outside is thin and if the cabin loses pressurization, the occupants can become hypoxic very quickly. Descending lowers the outside atmospheric pressure and allows the cabin to re-establish breathable conditions and stabilized pressurization.

Descent is the fastest and most reliable way to restore a safe environment, after which you can assess the cause, coordinate a diversion if needed, and declare an emergency if the situation warrants. Trying to keep cruising altitude and troubleshoot at altitude keeps you in a dangerous state longer, increasing hypoxia risk. Shutting off or pulling circuit breakers to the pressurization system isn’t a sanctioned first step and can complicate the situation, while simply continuing to cruise and troubleshoot bypasses the fundamental need to restore breathable air immediately.