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Aviation glossary

ICAO

International Civil Aviation Organization · Also: International Civil Aviation Organization, OACI

Registration and rules

Specialised agency of the United Nations that sets the standards and recommended practices for international civil aviation.

What it is

ICAO was created by the Chicago Convention of 1944 and became fully operational in 1947, when the Convention entered into force. Headquartered in Montreal, it counts almost every country in the world among its member states. It does not certify or inspect aircraft itself: its role is to agree common standards, which states then write into their own legislation.

Those standards are gathered in the Annexes to the Convention, covering everything from pilot licensing and aircraft registration to aerodromes, accident investigation and safety management. ICAO also assigns the four-letter airport codes, three-letter airline designators and aircraft type designators used in flight plans. It should not be confused with IATA, which is an association of airlines.

Related terms

Chicago ConventionInternational treaty signed in 1944 that sets out the principles of international civil aviation and gave rise to ICAO. IATATrade association representing a large share of the world's airlines, which sets common commercial and operational standards for air transport. ICAO airport codeFour-letter code under the ICAO system that identifies an aerodrome in flight plans, air traffic control and weather reports, such as EGLL for London Heathrow. ICAO airline designatorThree-letter designator that ICAO assigns to an aircraft operator for use in flight plans and air traffic control, such as BAW for British Airways. ICAO Annex 13ICAO’s international standard setting out how civil aviation accidents and incidents are investigated, with the sole aim of preventing future ones.
Whole glossary

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This page was last updated on October 9, 2026

APA

Vuelopedia. (2026, October 9). ICAO. Retrieved October 16, 2026, from https://vuelopedia.org/en/glossary/icao

MLA

“ICAO.” Vuelopedia, Fundación Poderia, 9 Oct. 2026, vuelopedia.org/en/glossary/icao. Accessed 16 Oct. 2026.

Chicago

Vuelopedia. “ICAO.” Fundación Poderia. Last modified October 9, 2026. https://vuelopedia.org/en/glossary/icao.

Harvard

Vuelopedia (2026) ICAO. Available at: https://vuelopedia.org/en/glossary/icao (Accessed: 16 October 2026).

BibTeX

@misc{vuelopedia_en_glossary_icao,
  author       = {{Vuelopedia}},
  title        = {{ICAO}},
  publisher    = {Fundación Poderia},
  year         = {2026},
  date         = {2026-10-09},
  url          = {https://vuelopedia.org/en/glossary/icao},
  howpublished = {\url{https://vuelopedia.org/en/glossary/icao}},
  urldate      = {2026-10-16},
  note         = {Accessed 2026-10-16}
}

Wikipedia

{{cite web |url=https://vuelopedia.org/en/glossary/icao |title=ICAO |website=Vuelopedia |publisher=Fundación Poderia |date=2026-10-09 |access-date=2026-10-16 |language=en}}

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