AFTN (Aeronautical Fixed Telecommunication Network) is a worldwide 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. AFTN is comprised of aviation entities including, ANS service providers, aviation service providers, airport authorities and government agencies, to name a few. It exchanges vital information for aircraft operations such as distress messages, urgency messages, flight safety messages, meteorological messages, flight regularity messages and aeronautical administrative messages. Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ...

AFTN addresses are 8 characters long and comprise of the 4-letter ICAO station code and 4-letter facility code. ZTZX refers to Control Tower, ZPZX refers to Approach Control Centre and ZQZX refers to Area Control Centre. SITA teletype addresses are 7 characters long. The International Civil Aviation Organization (ICAO), an agency of the United Nations, develops the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. ... Approach control refers to a control station in an air operations control center, helicopter direction center, or carrier air traffic control center, that is responsible for controlling air traffic as it transitions from control by an en-route control center and enters a terminal area. ... SITA (originally an acronym for Société Internationale de Télécommunications Aéronautiques) is a multinational information technology company specialising in providing IT services to the aviation industry. ...

Messages can be given a message priority to ensure best use of the system. SS relates to a Mayday priority, DD an Urgency priority, FF and GG a normal priority and KK a low priority.

and also priorities

SS= accidents GG= important events FF= Flight messeges (FPL, DLA, ARR etc.) KK= other ant compant messages

The AFTN system is backwards compatible with older transmission technology as many member states do not upgrade their AFTN centers fast enough. The format of a message betrays the heavy use of radio teletypes. A typical message would look like:

ZCZC DFA05 12032006 DD RCTPZQZX 1209 VTBBZQZX

MESSAGE

NNNN

The ZCZC stands for start of message and is geared towards torn-tape stations where the Z and c characters will punch all five holes on the tapes providing a quick check to the operator that the tape-puncher is working correctly. The NNNN similar is a familiar one hole consecutive sequence which can be quickly identified as end of message by operators.

 The message routing is easily automated by general purpose computers. Teletype communication with airline operators is sometimes maintained by having a connection to the SITA network which uses a 7 character address. 

The whole communications system is still rooted in the 'official' nature of radio teletypes.