What action should a student take for aircraft outside of sector 66 at FL180 when it is not usable?

The correct approach for managing aircraft outside of sector 66 at FL180 when it is not usable is to take action to ensure the aircraft enters sector 66 with a usable altitude. This is important for maintaining safety and operational efficiency within airspace management.

When managing air traffic, especially in sectors where altitude usability is a concern, it's crucial to ensure that aircraft are safely directed into airspace where they can operate effectively. Taking proactive steps to guide an aircraft into a sector with a usable altitude helps prevent potential conflicts or safety risks. This may involve coordinating with other air traffic control units or providing alternative routing that allows the aircraft to safely descend or change altitude as needed.

Redirecting the flight to an alternate sector or contacting the aircraft directly could be options, but they do not directly ensure that the aircraft enters sector 66 at a suitable altitude. Ignoring the request is not an acceptable response as it could lead to potential airspace violations or unsafe flying conditions. Therefore, taking appropriate action to achieve a safe altitude in sector 66 is the most effective and responsible choice.