Industry bodies & codes Travel technology glossary

ICAO codeICAO airline designator and location indicator

Also called ICAO airline codeICAO airport codethree-letter designator3LDlocation indicatorfour-letter code

Definition

An ICAO code is an identifier set by the International Civil Aviation Organization for flight operations. Airlines have three-letter designators, such as UAE for Emirates, used in flight plans and air traffic control, and airports have four-letter location indicators, such as OMDB for Dubai International. They differ from IATA's commercial codes.

What ICAO code means

ICAO is the United Nations agency for civil aviation. Its Convention on International Civil Aviation was signed in Chicago on 7 December 1944, and the organisation came into being on 4 April 1947. Where IATA codes serve the commercial side (reservations, tickets, schedules), ICAO codes serve operations: flight planning, air traffic control and aeronautical information.

Airline designators are three letters, listed in ICAO Doc 8585, and are paired with a telephony designator that forms the radio call sign. ICAO says these are assigned through States, whose focal points approve requests, and warns they are not to be confused with IATA's two-letter reservations codes. British Airways, for example, is BAW with the call sign SPEEDBIRD.

Location indicators are four letters, listed in ICAO Doc 7910, which also shows the matching IATA code where one exists. The first letter marks a broad world region and the second usually a country: EG is the United Kingdom, so Heathrow is EGLL, and the contiguous United States uses K, giving KJFK. ICAO codes cover many airfields that have no IATA code at all.

Travel sellers mostly book with IATA codes, but ICAO codes appear in flight tracking, operational data feeds and some airline and airport APIs, so booking platforms often need to map between the two.

How ICAO code works

ICAO codes are maintained through ICAO and its member States, then published for operational use.

  1. A designator is requestedAn aircraft operator requests a three-letter designator and telephony designator through ICAO's online system.
  2. The State approvesThe request is forwarded to the focal point of the relevant State, which approves it before ICAO assigns it.
  3. Location indicators are setFour-letter indicators for aerodromes are allocated within each State's regional letter block and kept stable.
  4. Codes are publishedICAO publishes designators in Doc 8585 and location indicators in Doc 7910, which is updated quarterly.
  5. Systems use themFlight plans, air traffic control, aeronautical charts and flight tracking services use the ICAO codes.

ICAO code in practice

Airline or airportIATAICAOCall sign
EmiratesEKUAEEMIRATES
British AirwaysBABAWSPEEDBIRD
Biman Bangladesh AirlinesBGBBCBANGLADESH
LufthansaLHDLHLUFTHANSA
Dubai International AirportDXBOMDBn/a
London HeathrowLHREGLLn/a

ICAO designators and call signs for the airlines above are as listed in the US FAA's published register of ICAO three-letter designators. The pattern is easy to see in an illustrative case: a traveller books Emirates flight EK 1 from DXB, while air traffic control handles the same flight as UAE1 departing OMDB, called on the radio as EMIRATES ONE. The Heathrow code EGLL shows the regional structure, with E for northern Europe and G for the United Kingdom, followed by two letters for the airport itself.

Who uses it

AirlinesAirlines file flight plans and communicate with air traffic control using their ICAO designator and call sign.
Booking and travel platformsPlatforms that combine reservations with flight status or tracking data map ICAO codes back to the IATA codes used in bookings.
Airports and authoritiesAirports and civil aviation authorities use location indicators in aeronautical publications, charts and NOTAMs.
Business aviation and charterCharter brokers and private operators often work with ICAO codes because many smaller airfields have no IATA code.

Advantages and limitations

Advantages

  • Covers far more airfields than IATA codes, including non-commercial ones.
  • The regional letter structure makes many indicators readable at a glance.
  • Three-letter airline designators give a larger, more distinct set than two-character codes.
  • Links each airline to a spoken call sign for clear radio communication.

Limitations

  • ICAO and IATA codes rarely match, so systems must hold and maintain mappings.
  • Most travellers and booking tools do not recognise ICAO codes.
  • Call signs can differ completely from the airline's commercial name.
  • Full ICAO code documents are sold, so free official lookups are limited.

Frequently asked questions about ICAO code

What is the difference between IATA and ICAO codes?

IATA codes are commercial: two-character airline codes and three-letter airport codes used for reservations, tickets and bag tags. ICAO codes are operational: three-letter airline designators and four-letter airport indicators used in flight plans and air traffic control. Emirates, for example, is EK to IATA and UAE to ICAO.

Why do US airport ICAO codes start with K?

ICAO location indicators start with a letter for a world region, and the contiguous United States uses K. Many US indicators are simply K plus the three-letter code, such as KJFK. The FAA notes that adding K does not by itself create an official ICAO indicator, and Alaska and Hawaii use PA and PH instead.

What is an airline call sign?

A call sign is the spoken name pilots and controllers use on the radio, set by the airline's ICAO telephony designator. Some match the airline name, such as EMIRATES, while others do not: British Airways flights use SPEEDBIRD. The call sign is followed by the flight number in radio calls.

Does every airport have an ICAO code?

Most airports and many smaller airfields have an ICAO location indicator, which is why ICAO codes cover far more places than IATA codes. Some small strips have only a national identifier. Conversely, IATA can assign codes to rail and ferry stations that have no ICAO code because they are not aerodromes.

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Sources and further reading

  1. ICAO — Designators and indicators
  2. ICAO — Convention on International Civil Aviation (Doc 7300)
  3. FAA — JO 7340 Contractions, ICAO aircraft company three-letter identifiers and telephony designators
  4. FAA — ICAO location indicators (US assignments)
  5. IATA — Fact sheet: IATA location codes
  6. Aviatize — ICAO location indicator
  7. Economy Middle East — Why does Dubai International have two codes, DXB and OMDB?