During a loss of cabin pressurization at FL270, what is the immediate action if passengers are on board?

In the event of a loss of cabin pressurization at FL270, the immediate action required is to initiate an immediate descent. This is crucial because cabin pressurization loss can lead to hypoxia, where the body does not receive enough oxygen. At higher altitudes, the air contains less oxygen, increasing the risk to both passengers and crew if immediate corrective actions are not taken.

Descending to a lower altitude, typically below 10,000 feet, ensures that the air pressure is sufficient to provide adequate oxygen levels for safe breathing. This rapid descent is essential for the safety and well-being of those on board. It allows the cabin crew to manage the situation effectively and provide support to the passengers, including deploying supplementary oxygen if available and needed.

Staying at cruising altitude or ascending higher would exacerbate the situation, as it would further decrease the available oxygen and potentially lead to serious health issues. Requesting an emergency landing is a necessary follow-up action but is not the immediate response to the cabin pressurization failure; the priority must be the descent to a safer altitude first.