What should an ATC facility do if an aircraft does not contact them after an ALNOT is issued?

When an Alert Notice, or ALNOT, is issued and an aircraft does not make contact with the Air Traffic Control facility, the appropriate response is to start search procedures. This action is taken because the lack of communication from the aircraft can indicate potential emergencies, such as an in-flight problem or that the aircraft has gone off course.

Initiating search procedures is a critical step in ensuring the safety of the aircraft and its occupants. ATC must act under the assumption that assistance might be needed, and time is often of the essence in such situations. Promptly commencing search efforts can help locate the aircraft as quickly as possible, potentially saving lives.

In terms of the other choices, assuming the aircraft is fine undermines the seriousness of the situation where communication is absent. Informing the next airport may be a step to take later, but the priority should be on ensuring the safety of the flight first, making it a secondary concern. Notifying the pilot's home base could be part of the protocol, but again, it would typically follow the initiation of search efforts as the primary action after an ALNOT is issued. Thus, starting search procedures is the most immediate and appropriate action.