The airline teletype system uses teleprinters, which are electro-mechanical typewriters that can communicate typed messages from point to point through simple electric communications channels, often just pairs of wires. The most modern form of these devices are fully electronic and use a screen, instead of a printer. Historical development The airline industry began using teletypewriter technology in the early 1920s utilizing radio stations located at 10 airfields in the United States. The US Post Office and other US government agencies used these radio stations for transmitting telegraph messages. It was during this period that the first federal teletypewriter system was introduced in the United States to allow weather and flight information to be exchanged between air traffic facilities. While the use of physical teletypes is almost extinct, the message formats and switching concepts remain similar. In 1929, Aeronautical Radio Incorporated (ARINC) was formed to manage radio frequencies and license allocation in the United States, as well as to support the radio stations that were used by the emerging airlines, a role ARINC still fulfils today. ARINC is a private company originally owned by many of the world's airlines including American Airlines, Continental Airlines, British Airways, Air France, and SAS; it was acquired by Collins Aerospace in December 2013. In 1949, the Société Internationale de Télécommunication Aeronautique (SITA) was formed as a cooperative by 11 airlines: Air France, KLM, Sabena, Swissair, TWA, British European Airways, British Overseas Airways Corporation, British South American Airways, Swedish AB Aerotransport, Danish Det Danske Luftfartselskab A/S, and Norwegian Det Norske Luftfartselskap. Their aim was to enable airlines to be able to use the existing communications facilities in the most efficient manner. Morse code was the general means of relaying information between air communications stations prior to World War II. Generally, it was only necessary to relay a message between one or two stations. After World War II, there was an increase in the number of commercial aircraft operating, and these aircraft were capable of flying greater distances than in the past. As a result, the Aeronautical Fixed Telecommunication Network (AFTN) was implemented worldwide as a means of relaying the air traffic communications, sometimes through the use of radioteletype which had become common among military forces in the 1940s. The airline industry continues to use teletypewriter messages over ARINC, SITA or AFTN networks as a medium for communicating via messages to exchange operational information. Most teletypewriter messages