Chicago Convention and ICAO

The Chicago Convention, formally the Convention on International Civil Aviation, is the treaty on which international air law rests. It recognises each State's control of its own airspace, sets the basic rules that let civil aircraft cross borders, and created the International Civil Aviation Organization (ICAO), which turns those principles into detailed technical rules through the Annexes to the Chicago Convention. Almost every State is party to it: ICAO has 193 Member States.

Pilots rarely read the Convention, but every rule they fly by traces back to it. SERA in Europe transposes the rules of the air of Annex 2, and the FAA applies the same Annex with differences it has notified; licences follow Annex 1; aircraft carry the documents listed in Article 29; and where a State departs from ICAO, its AIP says so. Air law papers in the EASA and FAA syllabuses start here.

Origins of the Chicago Convention

The Convention was drawn up at the International Civil Aviation Conference held in Chicago towards the end of the Second World War, when governments expected a large expansion of civil flying once peace returned. It was signed on 7 December 1944 by 52 States and came into force on 4 April 1947, when ICAO came into being. Its text, with later amendments, is published by ICAO as Doc 7300.

The Conference could agree safety and technical rules but not the commercial rights of airlines. Two separate agreements signed at Chicago dealt with those: the International Air Services Transit Agreement and the International Air Transport Agreement (see freedoms of the air).

ICAO is a specialised agency of the United Nations, with its headquarters in Montreal and seven regional offices, among them Paris for Europe. It is an intergovernmental body: its members are States, not airlines, and it issues no licences and certifies no aircraft itself.

Sovereignty and territorial airspace

Article 1 recognises that every State has complete and exclusive sovereignty over the airspace above its territory. Exam texts define sovereignty of airspace as the right of a State to impose its national law on the users of its territorial airspace. Under Article 2, a State's territory is the land areas and adjacent territorial waters under its sovereignty, suzerainty, protection or mandate; under the modern law of the sea, territorial waters extend up to 12 NM from the coast. Suzerainty in that list is, in its ordinary legal sense, the control one State exercises over the external affairs of a territory that otherwise governs itself. ATPL question banks built on the CAE Oxford texts use a different definition, contrasting it with sovereignty as a State's acceptance of the rules agreed at international conventions.

Beyond territorial waters lie the high seas, where no State is sovereign. There Article 12 applies the rules of the air established under the Convention, the Annex 2 rules, without exception. Within its territory each State keeps its own rules of the air, but undertakes to keep them as uniform as possible with ICAO's.

The Convention applies only to civil aircraft. Aircraft used in military, customs and police services are state aircraft, which may fly over or land in another State only by special agreement or other authorisation (Article 3). Munitions of war may not be carried in or above a State's territory without its permission, and each State may regulate or prohibit the use of cameras in aircraft over its territory.

Key Articles for Pilots

A Contracting State is a State party to the Convention; ICAO now calls them Member States. The articles most often examined are these:

ICAO Assembly, Council and ANC

The ICAO Assembly is the sovereign body. Every Contracting State has one vote, decisions are taken by a majority of votes cast, and the Assembly is convened by the Council and meets at least once every three years. It elects the Council, sets policy and votes the budget.

The ICAO Council is the permanent governing body, responsible to the Assembly. Its members are Contracting States elected by the Assembly for three years. For many years there were 36 of them, the figure used in most question banks; a 2016 amendment raising the number to 40 entered into force on 12 June 2026, and an extraordinary Assembly was called for November 2026 to elect the four additional members. The Council adopts the SARPs, approves the PANS, and settles disputes between States.

The Air Navigation Commission (ANC) is a body of experts, nominated by Contracting States and appointed by the Council, that examines proposals and presents SARPs to the Council for adoption. An amendment in force from the same date enlarged it from 19 to 21 members. The Secretariat, headed by the Secretary General, supports all three.

SARPs, PANS and Regional Procedures

Standards and Recommended Practices (SARPs) are adopted by the Council, by a two-thirds majority, and published as Annexes. A Standard is a specification whose uniform application is necessary for safety or regularity: States follow it or notify a difference. A Recommended Practice is desirable, and States endeavour to follow it; AIPs such as France's mark the Recommended Practices in their lists of differences with an asterisk. SARPs are not directly binding on individuals: they become law only when a State writes them into its national regulations, as the EU does in its implementing rules (see EASA regulatory framework).

Procedures for Air Navigation Services (PANS) are approved, not adopted, by the Council. They set out procedures in more detail than the SARPs and are recommended for worldwide use. The best known are:

• PANS-ATM (ICAO Doc 4444), the procedures of air traffic management, which complement Annexes 2 and 11. Older texts call it by its former name, PANS-RAC;
• PANS-OPS (Doc 8168), in two volumes: flight procedures for pilots, and the construction of visual and instrument procedures for designers.

Some procedures apply in one region only. ICAO divides the world into air navigation regions, such as EUR, NAT, AFI and PAC, and arrangements particular to a region are settled by Regional Air Navigation (RAN) agreements. The Regional Supplementary Procedures (ICAO Doc 7030) are approved by the Council and apply alongside PANS in the region concerned; on the North Atlantic, for example, they sit next to NAT Doc 007. RNP values for a State's airspace are likewise prescribed on the basis of RAN agreements.

Filing Differences Under Article 38

No State is forced to accept a Standard. Under Article 38, a State that finds it impracticable to comply in all respects, or that adopts regulations differing from a Standard, must notify ICAO of the differences immediately, and ICAO passes them to all other States. The filing of differences is how the system stays honest: a State may be stricter than ICAO, may meet the aim by other means, or may fall short, but it must say so.

The State then publishes its significant differences in its AIP, in GEN 1.7. France's GEN 1.7, for example, records that France does not require the ILS reference datum of a Category I facility to be at 15 m (50 ft), and that the European rule requiring data link communications to be recorded applies only to aeroplanes first issued with an individual certificate of airworthiness on or after 8 April 2014. Over the high seas no difference is possible.

The Annexes at a Glance

There are 19 Annexes, each identified by number and subject:

ICAO Annex 6 (Operation of Aircraft) is published in three parts: Part I for aeroplanes in international commercial air transport, Part II for international general aviation aeroplanes and Part III for helicopters. It contains the Standards behind air operator certificates, operations manuals, flight crew training and equipment carriage. ICAO Annex 19 (Safety Management), the most recent, gathers the safety management provisions of the other Annexes: each State runs a State safety programme, and operators, maintenance and training organisations, air navigation service providers and aerodromes run safety management systems.

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State of Registry, Operator and Design

Responsibility for an aircraft is shared between States, and one aircraft may involve four of them, designed in one, assembled in a second, registered in a third and flown by an operator of a fourth:

• The State of Registry is the State on whose register the aircraft is entered. It issues the certificates of registration and airworthiness, decides whether a damaged aircraft remains airworthy, and oversees continuing airworthiness. Annex 2 follows the aircraft wherever it bears that State's marks.
• The State of the Operator is the State where the operator has its principal place of business, or else its permanent residence. It issues the air operator certificate and approves the operator's training programme under Annex 6.
• The State of Design has jurisdiction over the organisation responsible for the type design. It must ensure a structural integrity programme exists for aeroplanes over 5,700 kg, and is told when another State first registers one of its aircraft.
• The State of Manufacture has jurisdiction over the organisation responsible for final assembly.

Leasing complicates this, because an airline may operate an aircraft registered abroad. Article 83 bis, in force since 1997, lets the State of Registry transfer some of its functions and duties to the State of the Operator by agreement. After an accident, the State of Occurrence investigates, or the State of Registry if the accident happens outside any State's territory, and the others may take part (see accident and incident investigation).

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.