In a yellow-level emergency, what action is not required?

In a yellow-level emergency, which typically indicates a potential or developing situation that may require specific actions, preparing the cabin for an evacuation is not a required action at this stage. This level of emergency suggests that while there may be some level of concern on the flight, the need for an immediate evacuation is not imminent. Therefore, the focus is more on assessing the situation and maintaining safety without jumping directly into emergency protocols designed for more severe situations.

The other actions, such as diverting to an alternate airport, conducting a priority landing, and ensuring cabin crew readiness, align with the overall standard operating procedures in response to potential emergencies. These steps are about preparations and decisions that need to be made to ensure the safety of all onboard should the situation escalate. In contrast, preparing for an evacuation is reserved for more critical stages where an immediate evacuation is necessary, thus making it the action that is not required in a yellow-level emergency.