If excessive smoke is detected in the cabin, what must cabin crew do?

When excessive smoke is detected in the cabin, the cabin crew's immediate priority is to ensure the safety of all onboard, which includes appropriately notifying the Pilot in Command. Advising the Pilot in Command allows for the proper assessment of the situation and decision-making regarding the best course of action. Opening the flight deck door in such a scenario could pose serious risks to both the crew and the cockpit environment, potentially exposing the flight deck to the same hazards present in the cabin.

The focus should be on maintaining clear communication with the flight deck so that the pilots can manage the situation effectively while following established protocols for smoke or fire. This decision prioritizes safety over impulse actions that could complicate the emergency response or endanger the flight crew and passengers. Other answers may suggest actions that either compromise safety or do not directly address the immediate need to communicate with the pilots about the smoke situation.