The Air Navigation Commission (ANC) is the technical body within ICAO. The commission is composed of 19 commissioners, nominated by the ICAO's contracting states and appointed by the ICAO Council.[5] Commissioners serve as independent experts, who although nominated by their states, do not serve as state or political representatives. InternationalStandards and Recommended Practices are developed under the direction of the ANC through the formal process of ICAO Panels. 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.
In the early 20th Century, theInternational Telecommunication Union met to discuss and implement one of the first internationally agreed upon standards relating to aviation, country-specific prefixes for aircraft callsigns. The first convention was held in 1903 in Berlin,Germany, but no agreements were reached among the eight countries that attended. At the second convention in 1906, also held in Berlin, twenty-seven countries attended.[6] The third convention, held in London in 1912, allocated the first radiocallsigns for use by aircraft. Following this, at theParis Convention of 1919, a forerunner to ICAO named ICAN was established, theInternational Commission for Air Navigation. ICAN continued to operate until 1945.[7][8]
TheConvention on International Civil Aviation, also known as the Chicago Convention, inChicago, was signed by 52 countries on 7 December 1944. Under its terms, aProvisional International Civil Aviation Organization was to be established, to be replaced in turn by a permanent organization when twenty-six countries ratified the convention. PICAO began operating on 6 June 1945, replacing ICAN. The 26th country ratified the convention on 5 March 1947 and, consequently, PICAO held its last session from 29 April 1947 until 7 May 1947, with the Convention on International Civil Aviation coming into force on 4 April 1947.[9]
In April 2013,Qatar offered to serve as the new permanent seat of the Organization. Qatar promised to construct a massive new headquarters for ICAO and to cover all moving expenses, stating that Montreal "was too far from Europe and Asia", "had cold winters", was hard to attend due to the Canadian government's slow issuance of visas, and that the taxes imposed on ICAO by Canada were too high.[11] According toThe Globe and Mail, Qatar's invitation was at least partly motivated by the pro-Israel foreign policy of Canadian Prime MinisterStephen Harper.[12][13] Approximately a month later, Qatar withdrew its bid after a separate proposal to the ICAO's governing council to move the ICAO triennial conference to Doha was defeated by a vote of 22–14.[14][15][16]
In June 2014, theMontreal Metro station closest to the ICAO headquarters was renamedSquare-Victoria–OACI,[a] celebrating the 70th anniversary of ICAO's presence in Montreal.[17]
In January 2020, ICAO blocked severalTwitter users, includingthink-tank analysts,U.S. Congressional staff, and journalists, who mentionedTaiwan in tweets related to ICAO. Many of the tweets were related to theCOVID-19 pandemic and Taiwan's exclusion from ICAO safety and health bulletins due to pressure from China. In response, ICAO issued a tweet stating that publishers of "irrelevant, compromising and offensive material" would be "precluded".[18][19][20]
Since that action, the organization has followed a policy of blocking anyone asking about it.[21][22]
In January 2020, Anthony Philbin, Chief of Communications for the ICAO Secretary General, defended ICAO's actions, stating, 'We felt completely justified in taking steps to protect the integrity of the information and discussions that our followers reasonably expect from our feeds.' In exchanges with the International Flight Network, Philbin refused to acknowledge the existence of Taiwan.[24]
On 1 February 2020, theUnited States Department of State issued a press release heavily criticizing ICAO's actions, characterizing them as "outrageous, unacceptable, and not befitting of a UN organization."[25][26]
On 2 May 2025, the ICAO Council expressed grave concern over ongoing Global Navigation Satellite System (GNSS) radio frequency interference in the Incheon Flight Information Region (FIR), incidents that have persisted since 2 October 2024, and are attributed toNorth Korea, officially known as the Democratic People's Republic of Korea (DPRK). The Council emphasized that such interference endangers international air navigation safety and violates the principles of the Chicago Convention. It strongly urged the DPRK to adhere to its international obligations and prevent future occurrences. Given the severity of the situation, the Council is considering reporting the matter to the 42nd Session of the ICAO Assembly in September 2025, as per Article 54(k) of the Convention, and will continue to monitor developments closely.[27]
DespiteLiechtenstein not being a direct party to ICAO, its government delegated Switzerland to enter into the treaty on its behalf in 1947, and the treaty is applicable in the territory of Liechtenstein.[31]
The Republic of China was a founding member of ICAO. Following itsretreat to Taiwan, it was eventually replaced by thePeople's Republic of China as the legal representative of China in 1971.
In 2013, Taiwan was for the first time invited to attend the ICAO Assembly, at its 38th session, as a guest under the name of "Chinese Taipei". As of September 2019[update], it has not been invited to participate again, due to renewed PRC pressure.[32][33][34][35]
The host government, Canada, supports Taiwan's inclusion in ICAO. Support also comes from Canada's commercial sector with the president of the Air Transport Association of Canada saying in 2019 that "It's about safety in aviation so from a strictly operational and non-political point of view, I believe Taiwan should be there."[36]
The ICAO Council is elected by the Assembly every three years and consists of 36 members elected in three groups. The present council was elected in October 2022.[37]The structure of the present Council is as follows:
On September 27, 2025, the ICAO Assembly held fresh elections to Group I and Group II of the Council and elected the following states for a three-year term. Elections to Group III were held on September 30:[38]
Meeting room of ICAO's Air Navigation Commission in July 2013
The Air Navigation Commission (ANC) is the ICAO Council technical executive body in charge of 17 of the 19 Annexes to the Chicago Convention. ANC develops and recommendICAO minimal standards that are related to these Annexes. To review and/or finalize the ongoing developments the commission meets for three sessions per year. Each session normally considers a number of documents being developments of ANC expert Panels. The ANC is composed of nineteen commissioners nominated by ICAO States in various aviation domains. However, legally these commissioners do not represent the interest of their State or any particular State or region. They have to conduct independently in the interest of the entire international civil aviation community. Additionally, several other representatives from ICAO States and up to eight members from the civil aviation industry may be invited to take part in ANC meetings as observers.[40][41]
Each country should have an accessibleAeronautical Information Publication (AIP), based on standards defined by ICAO, containing information essential toair navigation. Countries are required to update their AIP manuals every 28 days and so provide definitive regulations, procedures and information for each country aboutairspace and airports. ICAO's standards also dictate that temporary hazards to aircraft must be regularly published usingNOTAMs.
ICAO defines anInternational 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. This is useful in calibrating instruments and designing aircraft.[42] The standardized pressure is also used in calibrating instruments in-flight, particularly above thetransition altitude.
ICAO has published standards formachine-readable passports.[44] Machine-readablepassports have an area where some of the information otherwise written in textual form is also written as strings of alphanumeric characters, printed in a manner suitable foroptical character recognition, which enables border controllers and other law enforcement agents to process such passports more quickly without having to enter the information manually into a computer.
ICAO's technical standard for machine-readable passports is contained in Document 9303Machine Readable Travel Documents.[45]
A more recent standard coversbiometric passports. These containbiometrics to authenticate the identity of travellers. The passport's critical information is stored on a tinyRFID computer chip, much like information stored onsmart cards. Like some smart cards, the passport book design calls for an embedded contactless chip that is able to holddigital signature data to ensure the integrity of the passport and the biometric data.
ICAO uses4-letter airport codes (vs.IATA's 3-letter codes). 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, whereL indicates Southern Europe,F, France,PG, Paris de Gaulle, whileOrly Airport has the code LFPO (the 3rd letter sometimes refers to the particularflight information region (FIR) or the last two may be arbitrary). In most parts of the world, ICAO and IATA codes are unrelated; for example,Charles de Gaulle Airport has an IATA code of CDG. However, the location prefix for the continental United States isK, and ICAO codes are usually the IATA code with this prefix. For example, the ICAO code forLos Angeles International Airport is KLAX. Canada follows a similar pattern, where a prefix ofC is usually added to an IATA code to create the ICAO code. For example,Calgary International Airport is YYC or CYYC. (In contrast, airports inHawaii are in the Pacific region and so have ICAO codes that start withPH;Kona International Airport's code is PHKO. Similarly, airports inAlaska have ICAO codes that start withPA.Merrill Field, for instance is PAMR.) Not all airports are assigned codes in both systems; for example, airports that do not have airline service do not need an IATA code.
ICAO also assigns three-letterairline codes versus the more-familiar two-letter IATA codes—for example,UAL vs.UA forUnited Airlines. ICAO also providestelephony 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. For example, the identifier forJapan Airlines International isJAL and the designator isJapan Air, butAer Lingus isEIN andShamrock. Thus, a Japan Airlines flight numbered 111 would be written as "JAL111" and pronounced "Japan Air One One One" on the radio, while a similarly numbered Aer Lingus would be written as "EIN111" and pronounced "Shamrock One One One". In the US, FAA practices[49] require the digits of the flight number to be spoken in group format ("Japan Air One Eleven" in the above example) while individual digits are used for the aircraft tail number used for unscheduled civil flights.
ICAO is also responsible for issuing two to four characteralphanumeric aircraft type designators for those aircraft types which are most commonly provided with air traffic service. These codes provide an abbreviated aircraft type identification, typically used inflight plans. For example, theBoeing 747-100, -200 and -300 are given the type designatorsB741,B742 andB743 respectively.[50]
Non-SI units have been permitted for temporary use since 1979,[53] but a termination date has not yet been established, which would completemetrication of worldwide aviation,[54] and the following units are still in widespread use within commercial aviation:
inches of mercury are used in Japan and North America to measure pressure, although sometimesMETAR at Japanese airports show onlyhPa.[54]
Aviation in Russia and China currently uses km/h for reporting airspeed, and many present-day European glider planes also indicate airspeed in kilometres per hour.[55] China[54] and North Korea[54] use metres for reporting altitude when communicating with pilots.[54] Russia also formerly used metres exclusively for reporting altitude, but in 2011 changed to feet for high altitude flight. From February 2017, Russian airspace started transitioning to reporting altitude in feet only.[54] Runway lengths are now commonly given in metres worldwide, except in North America where feet are commonly used.[54]
The following table summarizes units commonly used in flight and ground operations and their recommended replacement.[52] A full list of recommended units can be found in annex 5 to the Convention on International Civil Aviation.[52]
Celsius is used for aviation weather reporting globally.Fahrenheit (°F) may be used for displaying, controlling, and documenting system temperatures (HVAC, engine) on older North American aircraft.
Hectopascals are mostly used in aviation worldwide, while inches of mercury are used in Japan and North America.[54] One hectopascal is equal to one millibar.
Reported in metres for most of the world. Visibility over 5000 m may be given in kilometres.[52] Canadian, American, and Mexican airports usestatute miles, or feet when reporting laser measurements.[54]
Used forfuel tank capacity of an aircraft. Unit varies depending on the gauges fitted to the aircraft. The most common current unit is kilograms.[citation needed]
Used for cargo capacity, fuel capacity,gross mass,payload.Tonne may also be used for gross mass and payload.[52] Tons are often used informally duringflight planning to gauge approximate weights. Ton then usually either refers to thetonne, or thelong ton orshort ton which differ from the tonne by about 2% and 10% respectively.
Measured with anattitude indicator, and are always presented in degrees. (Sensors, data and calculations may however use a mix of degrees andradians, as many scientists and engineers prefer to work with radians.)
This section'sfactual accuracy may be compromised due to out-of-date information. Please help update this article to reflect recent events or newly available information.(February 2009)
Emissions from international aviation are specifically excluded from the targets agreed under theKyoto Protocol. Instead, the Protocol invites developed countries to pursue the limitation or reduction of emissions through the International Civil Aviation Organization. ICAO's environmental committee continues to consider the potential for using market-based measures such as trading and charging, but this work is unlikely to lead to global action. It is currently developing guidance for states who wish to include aviation in anemissions trading scheme (ETS) to meet their Kyoto commitments, and for airlines who wish to participate voluntarily in a trading scheme.[citation needed]
Emissions from domestic aviation are included within the Kyoto targets agreed by countries. This has led to some national policies such as fuel and emission taxes for domestic air travel in the Netherlands and Norway, respectively. Although some countries tax the fuel used by domestic aviation, there is no duty onkerosene used on international flights.[59]
On 6 October 2016, the ICAO finalized an agreement among its 191 member nations to address the more than1000 million tonnes of carbon dioxide emitted annually by international passenger and cargo flights. The agreement will use an offsetting scheme called CORSIA (the Carbon Offsetting and Reduction Scheme for International Aviation) under which forestry and other carbon-reducing activities are directly funded, amounting to about 2% of annual revenues for the sector. Rules against 'double counting' should ensure that existingforest protection efforts are not recycled. The scheme did not take effect until 2021 and will be voluntary until 2027, but many countries, including the US and China, have promised to begin at its 2020 inception date. Under the agreement, the global aviation emissions target is a 50% reduction by 2050 relative to 2005.[61]NGO reaction to the deal was mixed.[62][63][64]
The agreement has critics. It is not aligned with the 2015 Paris climate agreement, which set the objective of restricting global warming to 1.5 to 2 °C. A late draft of the agreement would have required the air transport industry to assess its share of global carbon budgeting to meet that objective, but the text was removed in the agreed version.[65][66] CORSIA will regulate only about 25 percent of aviation's international emissions, since it grandfathers all emissions below the 2020 level, allowing unregulated growth until then.[67] Only 65 nations will participate in the initial voluntary period, not including significant emitters Russia, India and perhaps Brazil. The agreement does not cover domestic emissions, which are 40% of the global industry's overall emissions.[66] One observer of the ICAO convention made this summary:
Airline claims that flying will now be green are a myth. Taking a plane is the fastest and cheapest way to fry the planet and this deal won't reduce demand for jet fuel one drop. Instead offsetting aims to cut emissions in other industries,
although another critic called it "a timid step in the right direction."[68]
ICAO has expressed strong opposition to 2025 proposals from various UN bodies and international organizations, including the International Monetary Fund, suggesting new taxes or levies on international aviation to fund global climate initiatives. ICAO contends that such measures could undermine CORSIA, emphasizing that CORSIA is the sole global framework for addressing international aviation emissions and warning that additional levies could disrupt its implementation and the broader goal of sustainable aviation development. While acknowledging the need for increased climate finance, ICAO urged stakeholders to support existing mechanisms like CORSIA rather than introducing potentially conflicting financial measures.[69]
Most air accident investigations are carried out by an agency of a country that is associated in some way with the accident. For example, theAir Accidents Investigation Branch conducts accident investigations on behalf of theBritish Government. ICAO has conducted four investigations involving air disasters, of which two were passenger airliners shot down while in international flight over hostile territory.
UTA Flight 772, which was destroyed by a bomb on 19 September 1989 above theSahara Desert in Niger, en route fromN'Djamena, Chad, to Paris, France. The explosion caused the aircraft to break up, killing all 156 passengers and 15 crew members, including the wife of U.S. AmbassadorRobert L. Pugh. Investigators determined that a bomb placed in the cargo hold by Chadian rebels backed byLibya was responsible for the explosion. A French court convictedin absentia six Libyans of planning and implementing the attack.[72]
The 1996 shootdown of Brothers to the Rescue aircraft on 24 February 1996, when two civilian aircraft operating north of Cuba were shot down by two jets of theCuban Air Force. The Cuban military alleged that aircraft operated by the groupBrothers to the Rescue had scattered propaganda leaflets onto Cuba prior to the incident, and issued orders that such aircraft be shot down. All four crew members aboard the two aircraft were killed, whilst a third aircraft managed to escape and return to the American mainland.
ICAO is looking at having a singular ledger for drone registration to help law enforcement globally. Currently, ICAO is responsible for creating drone regulations across the globe, and it is expected that it will only maintain the registry. This activity is seen as a forerunner to global regulations on flying drones under the auspices of the ICAO.[73]
ICAO currently maintains the 'UAS Regulation Portal'[74] for various countries to list their country's UAS regulations and also review the best practices from across the globe.
^"Member States.English.pdf"(PDF). ICAO.Archived(PDF) from the original on 5 June 2015. Retrieved20 July 2014.The Minister of Switzerland made the following statement in the note transmitting the Swiss Instrument of Ratification:"My Government has instructed me to notify you that the authorities in Switzerland have agreed with the authorities in the Principality of Liechtenstein that this Convention will be applicable to the territory of the Principality as well as to that of the Swiss Confederation, as long as the Treaty of 29 March 1923 integrating the whole territory of Liechtenstein with the Swiss customs territory will remain in force".
^Council action in pursuance of Assembly Resolution A22-18 adopted 23 March 1979:[..]to cover all aspects of air and ground operations; provision of standardized system of units based on the SI; identification of non-SI units permitted for use in international civil aviation; provision for termination of the use of certain non-SI units.
