I
In the early 1980s ICAO introduced the current three-letter-system due to the
increasing number of airlines. It became the official new standard system in
November 1987.
An example is:
•
Operator: American Airlines
•
Three-letter designator: AAL (the original ICAO-two-letter-
designator AA was used until 1987 and is also the IATA code of the airline)
•
Telephony designator: AMERICAN
Certain combinations of letters, for example SOS, are not allocated to avoid confusion with
other systems. Other designators, particularly those starting with Y and Z, are reserved for
government organizations.
The designator YYY is used for operators that do not have a code allocated.
Call signs (flight identification or flight ID)
Most airlines employ a call sign that is normally spoken during airband radio transmissions.
As by ICAO Annex 10 chapter 5.2.1.7.2.1 a call sign shall be one of the following types:
•
Type A: the characters corresponding to the registration marking of the aircraft.
•
Type B: the telephony designator of the aircraft operating agency, followed by the last
four characters of the registration marking of the aircraft.
•
Type C: the telephony designator of the aircraft operating agency, followed by the
flight identification.
The one most widely used within commercial aviation is type C.
The flight identification is very often the same as the flight number, though this is not always
the case.
In case of call sign confusion a different flight identification can be chosen, but the flight
number will remain the same. Call sign confusion happens when two or more flights with
similar flight numbers fly close to each other, e.g., KLM 645 and KLM 649 or Speedbird 446
and Speedbird 664.
A - Z of Flight
June 2017
www.alliance-airways.net
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