Ground Visibility
The visibility at an aerodrome, as reported by an accredited observer.
Location Indicator
A four-letter code group formulated in accordance with the rules prescribed by ICAO and assigned to the location of an aeronautical fixed station.
Aeronautical Fixed Station
A station in aeronautical fixed service.
AFS
Aeronautical Fixed Service
A telecommunication service between specified fixed points provided primarily for the safety of air navigation and for the regular, efficient and economical operation of air traffic.
AFTN
Aeronautical Fixed Communication Network
A world-wide system of aeronautical fixed circuits provided, as part of the aeronautical fixed service, for the exchange of messages and/or digital data between aeronautical fixed stations having the same or compatible communications characteristics.
Prohibited Area
An airspace to defined dimensions, above the land areas or territorial waters of a state, within which the flight of aircraft is prohibited.
Restricted Area
An airspace of defined dimensions, above the land areas or territorial waters of a state, within which the flight of aircraft is restricted in accordance with certain specific conditions.
Danger Area
An airspace of defined dimensions within which activities dangerous to the flight of aircraft may exist at specific times.