Regardless of mission classification, who is responsible for notifying appropriate approach control facilities of approved ALTRVs?

The responsibility for notifying appropriate approach control facilities of approved Alternate Routes (ALTRVs) primarily lies with ARTCCs (Air Route Traffic Control Centers). ARTCCs play a crucial role in managing air traffic across large geographic areas and are specifically tasked with coordinating how aircraft will navigate through their designated airspace.

When an ALTRV is established, it's essential that the relevant approach control facilities are informed to ensure that they can manage incoming and outgoing air traffic effectively, thereby maintaining safety and efficiency within the airspace. ARTCCs have the communication infrastructure and authority to carry out these notifications, ensuring all necessary stakeholders are aware of the approved routes.

The other choices involve entities that have different roles—Flight Service Stations provide flight planning and advisory services but do not typically handle ALTRV notifications, Local Ground Control deals with taxiing and runway operations at an airport and wouldn't be involved in the broader air route management, and while all aircraft should be aware of ALTRVs for their navigation, they do not have the authority to notify control facilities. Hence, ARTCCs are the correct answer because of their centralized role in air traffic control.