Which category of NOTAM concerns navigational facilities and airports?

The category of NOTAM that concerns navigational facilities and airports is the D NOTAM. These NOTAMs provide essential information regarding the status of airports, air navigation facilities, and other critical factors affecting flight operations. They may include details about runway closures, changes in airspace structure, or updates to navigational aids, making them vital for pilots and aeronautical personnel to ensure safety and situational awareness during flight operations.

In contrast, FDC NOTAMs are issued to disseminate information that requires immediate attention, such as changes in procedures or airspace usage but do not focus specifically on navigational facilities or airports. Pointer NOTAMs are used to direct pilots to specific D NOTAMs, essentially functioning as references rather than providing direct information on navigational facilities. Military NOTAMs pertain to military operations and areas that may not be relevant to civilian flight activities. Therefore, D NOTAMs are specifically designed to inform about the state and availability of navigational aids and airports, which is why this choice is the correct one.