What is a critical command to give during a decompression event?

During a decompression event, the most critical command to give is to instruct passengers to "Grab a mask!" This is because, in the event of a sudden loss of cabin pressure, supplemental oxygen is essential for maintaining consciousness and preventing hypoxia, which is a dangerous condition that occurs when the body does not receive enough oxygen.

The emergency oxygen masks are located above each seat, and passengers need immediate guidance to don them quickly. This ensures that they receive the necessary oxygen while the crew manages the emergency situation and prepares for a potential descent to a safer altitude where breathable air is available.

While other commands like fastening seatbelts or checking surroundings can be important in different emergency situations, they are not as immediately critical as getting oxygen during a decompression. Engaging emergency landing procedures is also important but typically comes after ensuring that passengers are provided with adequate oxygen to maintain their safety and well-being during the incident.