What is the proper sequence during a cabin altitude warning after initiating descent?

• A. Inform ATC, then descend, and ignore QRH.
• B. Initiate rapid descent, inform ATC, deploy oxygen if required, and follow QRH.
• C. Initiate rapid descent, deploy oxygen if required, inform ATC, and follow QRH.
• D. Deploy oxygen if required, initiate rapid descent, inform ATC, and follow QRH.

Answer: (C)

When a cabin altitude warning occurs, the priority is to restore breathable air as quickly as possible. The immediate action is to initiate a rapid descent to a safe altitude, because reducing the cabin altitude quickly minimizes the time occupants could be exposed to hypoxia.

After you start the descent, provide oxygen if required to ensure crew and passengers have a reliable oxygen supply during the descent and continued workload. Once the descent and oxygen setup are underway, inform ATC to declare an emergency and receive priority handling.

Finally, follow the QRH procedures to manage the situation and work toward returning the aircraft to normal operations. This order—descend first, supply oxygen, notify ATC, then complete the QRH—prioritizes immediate safety and compliance over simply communicating or performing checks, which is why it’s the best sequence.