In the context of aviation and aerospace, an "Airport/Facility Directory" is a reference publication that provides detailed information about airports, airfields, and other aviation facilities. The directory contains a comprehensive list of airports, including their location, elevation, runway data, communications frequencies, navigation aids, fuel availability, and other relevant details.

The Airport/Facility Directory typically includes information such as:

1. Airport diagrams and layouts
2. Runway and taxiway data, including lengths, widths, and surface types
3. Instrument landing systems (ILS) and other navigation aids
4. Communication frequencies, including tower, ground, and approach control frequencies
5. Fuel availability, including types and locations of fuel facilities
6. Parking and servicing information, including tie-downs, hangars, and maintenance facilities
7. Weather information, including nearby weather reporting stations and forecasting services
8. Air traffic control procedures and regulations
9. Nearby airspace restrictions and special use airspace
10. Contact information for airport management, air traffic control, and other aviation services

The Airport/Facility Directory is an essential tool for pilots, air traffic controllers, and other aviation professionals, as it provides critical information for planning and executing safe and efficient flights. The directory is typically updated regularly to reflect changes in airport facilities, procedures, and regulations.

In the United States, the Federal Aviation Administration (FAA) publishes the Airport/Facility Directory, which is also known as the "A/FD." The A/FD is available in print and digital formats, and it is updated every 56 days to ensure that pilots and other users have access to the most current information.