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Aircraft Call-sign

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Article Information
Category: Air Ground Communication Air Ground Communication
Content source: SKYbrary About SKYbrary
Content control: EUROCONTROL EUROCONTROL

Alternatives: Aircraft Callsign, Aeroplane Call-sign, Airplane Call-sign, Airplane Callsign


Description

An aircraft call sign is a group of alphanumeric characters used to identify an aircraft in air-ground communications. (EUROCONTROL EATM Glossary of Terms)

The rules governing the use of aircraft call signs are laid down in ICAO Annex 10: Aeronautical Communications, Volume II - Communication Procedures, Chapter 5. Relevant paragraphs are summarised below.

Three different types of aircraft call sign may be encountered (see table below), as follows:

Type (a) The characters corresponding to the registration marking of the aircraft (e.g. ABCDE). The name of the aircraft manufacturer or model may be used as a prefix (e.g. Airbus ABCDE);
Type (b) The telephony designator of the aircraft operating agency, followed by the last four characters of the registration marking of the aircraft (e.g. Rushair BCDE);
Type (c) The telephony designator of the aircraft operating agency, followed by the flight identification (e.g. Rushair 1234).

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Flight identification may be the 'public' flight number used for ticketing and aircraft handling or it may be an alternative unique alphanumeric string. When Flight identification rather than aircraft identification is used, then it may not necessarily correspond to the "public" flight number used for passenger ticketing and aircraft ground handling and may instead be any alternative unique alphanumeric string.

Also, the "telephony designator of the aircraft operating agency" will, in airline use, be the designator of the company for whom the flight is being operated, which may not be the operator of the aircraft.

The full call sign must be used when establishing communications.

After satisfactory communication has been established, abbreviated call signs may be used provided that no confusion is likely to arise; however, an aircraft must use its full call sign until the abbreviated call sign has been used by the ground station.

Call signs may be abbreviated only in the manner shown below (see table above.)

Type (a) The first character of the registration and at least the last two characters of the full call sign (the name of the aircraft manufacturer or model may be used in place of the first character);
Type (b) The telephony designator of the aircraft operating agency, followed by at least the last two characters of the call sign;
Type (c) No abbreviated form.

Most airline call signs belong to type (c) for which there is no abbreviation. Therefore, abbreviations such as “1234” or “Rushair 34” are not permissible. An aircraft is not permitted to change its call sign during flight, except temporarily on the instruction of an air traffic control unit in the interests of safety.

In order to avoid any possible confusion, when issuing ATC clearances and reading back such clearances, controllers and pilots must always add the call sign of the aircraft to which the clearance applies.

Further Reading

HindSight Articles:

AGC Safety Letters:

EUROCONTROL Action Plan for Air-Ground Communications Safety, including: