The ICAO should not be confused with the International Air Transport Association ( IATA ), a trade organization for airlines also headquartered in Montreal, or with the Civil Air Navigation Services Organisation ( CANSO ), an organization for Air Navigation Service Providers ( ANSPs ) with its headquarters at Amsterdam Airport Schiphol in the Netherlands.

The ICAO defines an International Standard Atmosphere ( also known as ICAO Standard Atmosphere ), a model of the standard variation of pressure, temperature, density, and viscosity with altitude in the Earth's atmosphere.

ICAO also assigns 3-letter airline codes ( vs. the more-familiar 2-letter IATA codes — for example, UAL vs. UA for United Airlines ).

ICAO also provides telephony designators to aircraft operators worldwide, a one-or two-word designator used on the radio, usually, but not always, similar to the aircraft operator name.

ICAO is also responsible for issuing alphanumeric aircraft type codes containing two to four characters.

The NATO phonetic alphabet, more accurately known as the International Radiotelephony Spelling Alphabet and also called the ICAO phonetic or ICAO spelling alphabet, as well as the ITU phonetic alphabet, is the most widely used spelling alphabet.

San Luis Obispo County Regional Airport ( IATA: SBP, ICAO: KSBP, FAA LID: SBP ), also known as McChesney Field, is an airport located in San Luis Obispo, California serving San Luis Obispo County.

* Carbon County Airport, also known as PUC ( IATA code ) and KPUC ( ICAO code )

; LS: ICAO airport code or nationality letters for location indicator ( see also: List of airport codes: LS )

It will also use the letters EDDB, the current code for Berlin Schönefeld Airport, as its ICAO code.

Because of their isolation and difficulty of access, there are no human settlements on these islands, but a detachment of the Chilean Navy is stationed on Isla San Félix, which also hosts a runway ( ICAO code for the airfield: SCFX ).

ICAO codes are also used to identify other aviation facilities such as weather stations, International Flight Service Stations or Area Control Centers, whether or not they are located at airports.

Lalibela is also home to an airport ( ICAO code HALL, IATA LLI ), a large market, two schools and a hospital.

* China Southern Airlines, China, CSN is also their ICAO airline designator

Sibulan Airport ( IATA: DGT, ICAO: RPVD ) also known as Dumaguete Airport.

The airport facilities are also known as Istres-Le Tubé ( ICAO airport code: LFMI ).

* LEAP is also the ICAO code for Empuriabrava Airfield at Girona province in Spain.

The town is also home to an airport ( ICAO code HAGN, IATA GDQ ), and Gondar University which includes Ethiopia's main faculty of medicine.

The airport also attempts to adhere to the air transport standards established by the International Civil Aviation Organization ( ICAO ).

The Convention on International Civil Aviation, also known as the Chicago Convention, established the International Civil Aviation Organization ( ICAO ), a specialized agency of the United Nations charged with coordinating and regulating international air travel.

As more advanced communications methods, such as teleprinter and satellite, took over, the number of such stations diminished, but another type appeared that transmitted spoken and also seemingly random number and letter groups, the latter usually using words from a radio alphabet such as ICAO / NATO alphabet.

Northeim also provides a small grass airfield ( ICAO locator code: EDVN ) due east of the town.

ICAO standardizes machine-readable passports worldwide.

In some states a form of separation is provided to certain aircraft in uncontrolled airspace as far as is practical ( often known under ICAO as an advisory service in class G airspace ), but separation is not mandated nor widely provided.

Radio-navigation aids must keep a certain degree of accuracy ( set by international standards of CAST / ICAO ); to assure this is the case, flight inspection organizations periodically check critical parameters with properly equipped aircraft to calibrate and certify ILS precision.

Information below is based on ICAO, FAA and JAA ; certain states may have filed differences.

Radio-navigation aids must keep a certain degree of accuracy, given by international standards, FAA, ICAO, etc.

Radio-navigation aids must keep a certain degree of accuracy, given by international standards, FAA, EASA, ICAO, etc.

Higher levels of Air Traffic Advisory and Control services may be available within certain portions of airspace within a FIR, according to the ICAO class of that portion of airspace ( with regard to national regulations ), and the existence of a suitably equipped authority to provide the services.

The aircraft need not necessarily be equipped for flight under IFR, and the aircraft must remain clear of clouds with the surface in sight, and maintain a certain flight visibility minimum ( 1, 500 metres according to ICAO, one statute mile in the US, 1, 500 m visibility, in sight of surface and clear of cloud in Europe ).

Antarctic airports are subject to severe restrictions and limitations resulting from extreme seasonal and geographic conditions ; they do not meet ICAO standards, and advance approval from the respective governmental or nongovernmental operating organization is required for landing ( 1999 est.

* ASH, ICAO code for Mesa Airlines

Bank for International Settlements, Council of Europe, Central European Initiative, EBRD, United Nations Economic Commission for Europe, FAO, Group of 77, IAEA, IBRD, ICAO, International Criminal Court, International Development Association, IFAD, International Finance Corporation, IFRCS, ILO, International Monetary Fund, International Maritime Organization, Interpol, IOC, International Organization for Migration ( observer ), ISO, ITU, Non-Aligned Movement ( guest ), Organization of American States ( observer ), OIC ( observer ), OPCW, Organization for Security and Co-operation in Europe, Southeast European Cooperative Initiative, United Nations, UNCTAD, UNESCO, UNIDO, UNMEE, UPU, WHO, WIPO, WMO, WToO, WTrO ( observer )

In January 2011 the U. S. Federal Aviation Administration ( FAA ) assessed the Government of Croatia's Civil Aviation Authority announcing that Croatia complied with International Civil Aviation Organization ( ICAO ) aviation safety standards for oversight of Croatia's air carrier operations.

* CPD is the ICAO airline designator for Capital Airlines Limited ( Kenya )

* GIA, the ICAO code for Garuda Indonesia

The ICAO Council adopts standards and recommended practices concerning air navigation, its infrastructure, flight inspection, prevention of unlawful interference, and facilitation of border-crossing procedures for international civil aviation.

In addition, the ICAO defines the protocols for air accident investigation followed by transport safety authorities in countries signatory to the Convention on International Civil Aviation, commonly known as the Chicago Convention.

Once approved by the Commission, standards are sent to the Council, the political body of ICAO, for consultation and coordination with the Member States before final adoption.

The forerunner to the ICAO was the International Commission for Air Navigation ( ICAN ).

ICAO publishes Doc 9303 – Machine Readable Travel Documents, the technical standard for machine-readable passports.

The ICAO code is based on the region and country of the airport — for example, Charles de Gaulle Airport has an ICAO code of LFPG, where L indicates Southern Europe, F, France, PG, Paris de Gaulle, while Orly Airport has the code LFPO ( the 3rd letter sometimes refers to the particular flight information region ( FIR ) or the last two may be arbitrary ).

In most of the world, the ICAO and IATA codes are unrelated ; for example, Charles de Gaulle Airport has an IATA code of CDG and Orly, ORY.

However, the location prefix for continental United States is K and the ICAO codes are usually the IATA code with this prefix — for example, the ICAO code for LAX is KLAX.