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Max Planck Encyclopedia of Public International Law [MPEPIL]

Air Defence Identification Zones

J Ashley Roach

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2022. All Rights Reserved. Subscriber: null; date: 09 December 2022

Warfare, air — Civil aviation — Exclusive economic zone — Territorial sea — UNCLOS (UN Convention on the Law of the Sea)

Published under the auspices of the Max Planck Institute for Comparative Public Law and International Law under the direction of Professor Anne Peters (2021–) and Professor Rüdiger Wolfrum (2004–2020). 

A. Concept and Definitions

An Air Defence Identification Zone (‘ADIZ’) is a defined area of airspace within which civil aircraft are required to identify themselves. These zones are established above the exclusive economic zone (‘EEZ’) or high seas adjacent to the coast, and over the territorial sea, internal waters, and land territory. The legal basis for such zones is the right of States, under the Convention on International Civil Aviation of 1944 (Chicago Convention [1944]), to establish conditions and procedures for entry into their national airspace, ie, the airspace over their territory, territorial sea, and in the case of an archipelagic State, over its archipelagic waters (see para. 13 below). A declaration of an ADIZ does not constitute a claim of sovereign rights (Sovereignty). Accordingly, an aircraft approaching national airspace can be required to identify itself while seaward thereof in international airspace as a condition of entry approval.

An ADIZ is separate from a Flight Information Region (‘FIR’). A FIR is a specified region of airspace in which a flight information service and an alerting service (‘ALRS’) are provided. The International Civil Aviation Organization (ICAO) has divided the world into zones (‘Air Navigation Regions’) for the purpose of assisting and controlling civil aircraft to ensure safety of navigation. Each zone is subdivided into both FIRs and areas of ‘controlled airspace’. FIRs may embrace both national and international airspace. FIRs are delimited by Regional Air Navigation Agreements which are subject to the approval of the ICAO Council. These agreements are concluded in the framework of the Regional Conferences on Air Navigation. The Chicago Convention, its Annexes, and FIRs do not apply to State, including military, aircraft (Art. 3 Chicago Convention).

B. Historical Evolution of Legal Rules

Arts 1 and 2 Convention on the Territorial Sea and the Contiguous Zone ([done 29 April 1958, entered into force 10 September 1964] 516 UNTS 205) provide that the sovereignty of a coastal State extends beyond its land territory and internal waters, to an adjacent belt of sea described as the territorial sea, and that this sovereignty extends to the air space over the territorial sea. Art. 2 UN Convention on the Law of the Sea (Law of the Sea) confirms this rule and extends it, in the case of an archipelagic State, to its archipelagic waters. Under both treaties, aircraft do not enjoy the right of innocent passage over the territorial sea. Art. 2 (4) Convention on the High Seas ([done 29 April 1958, entered into force 30 September 1962] 450 UNTS 11) provides that all States have the ‘freedom to fly over the high seas’. Art. 87 (1) (b) UN Convention on the Law of the Sea confirms that all States, both coastal and land-locked (Land-Locked States), as part of the freedom of the high seas, have freedom of overflight of the high seas. Both treaties provide that these freedoms shall be exercised by all States with due regard for the interests of other States in their exercise of the freedom of the high seas. Art. 58 (1) UN Convention on the Law of the Sea provides that all States have freedom of overflight over the EEZ. Art. 58 (3) UN Convention on the Law of the Sea imposes a similar due regard obligation on them.

Art. 12 Chicago Convention provides in part that for aircraft flying over the high seas, the rules in force shall be those established under the Chicago Convention. Individual States have taken unilateral action with substantial practical effect on aircraft flying over the high seas (Unilateral Acts of States in International Law): temporary restrictions on the use of defined danger areas over the high seas (Safety Zones; Security Zones), and extension of traffic control, or air traffic identification, by a coastal State to areas adjacent to, but outside that State’s territorial airspace. Art. 11 Chicago Convention expressly recognizes the right of each State to establish laws and regulations relating to the admission to or departure from its territory of aircraft engaged in international air navigation (Air Law).

However, for safety and national defence purposes, aircraft operating in airspace adjacent to a State but not intending to enter that State’s airspace have been required to comply with identification and control procedures similar to those imposed by the adjacent State on aircraft intending to enter its airspace.

C. Current Legal Situation

There are no treaty provisions governing the establishment or operation of ADIZs per se. States that have established standing ADIZs include Canada, France, Japan, Republic of Korea, the United States, and Indonesia (over Java). Australia has, from time to time, declared an ADIZ for military exercise purposes. These unilateral claims have not been objected to and it may be presumed that the right to declare an ADIZ is now recognized as a right under customary international law.

D. Special Problems

ADIZ regulations promulgated by the States apply to aircraft bound for their territorial airspace and require the filing of flight plans and periodic position reports. The coastal State has no right to require a foreign aircraft to identify itself or otherwise to apply its ADIZ procedures if it does not intend to enter national airspace.

Failing voluntary identification, an aircraft can be expected to be identified by interceptor aircraft, and not be fired upon as a Soviet fighter aircraft did on 1 September 1983 against Korean Airline flight 007 when it strayed into Soviet airspace (Korean Air Lines Incident [1983]). As a result of this incident, Art. 3bis Chicago Convention was adopted in 1984 (Protocol relating to an Amendment [Article 3bis] to the Convention on International Civil Aviation) and the procedures for identification of civil aircraft have been set out in an attachment to the International Civil Aviation Organization Rules of the Air in implementation of Art. 3bis Chicago Convention (‘Attachment A: Interception of Civil Aircraft’ in Annex 2 to the Convention on International Civil Aviation: International Standards and Recommended Practices-Rules of the Air [ICAO 10th edn Montreal 2005] ATT A-1).

The declaration of an ADIZ does not confer on an intercepting pilot the right to engage an aircraft. The international law of self-defence (Self-Defence, Anticipatory) and national rules of engagement will provide guidance on the circumstances in which an aircraft may be engaged in peacetime.

10 It should be emphasized that the foregoing contemplates a peacetime or non-hostile environment. In the case of imminent or actual hostilities, a State may find it necessary to take measures in self-defence that will affect overflight in international airspace (Air Warfare).

11 The International Civil Aviation Organization (‘ICAO’) has considered whether the Chicago Convention should be amended to take into account developments in the law of the sea, including recognition of the status of the airspace over certain archipelagic waters as national airspace wherein foreign aircraft have the right of archipelagic sea lanes passage over archipelagic sea lanes. In its 1987 study of the implications of the UN Convention on the Law of the Sea on the Chicago Convention (ICAO Legal Committee, Secretariat Study ‘United Nations Convention on the Law of the Sea: Implications, if any, for the Application of the Chicago Convention, its Annexes and other International Law Instruments’ [ICAO document C-WP/7777 done 1984, reproduced 1987 as Working Paper LC/26-WP/5-1] reprinted in [1987] 3 NILOS Yearbook 243 para. 10.8) and other international air law instruments, the ICAO Secretariat concluded that there was no need for a textual amendment of the Chicago Convention, that Art. 2 Chicago Convention will have to be read as meaning that the territory of a State shall be the land areas, territorial sea adjacent thereto and its archipelagic waters. In 2008 the ICAO’s Legal Committee considered an Indonesian proposal to amend Art. 2 Chicago Convention to recognize the archipelagic State’s sovereignty over its archipelagic waters and superjacent airspace (ICAO Legal Committee, ‘Proposal to Amend Article 2 of the Chicago Convention’ [Working Paper LC/33-WP/4-7 ICAO Legal Committee 17 April 2008]). At the recommendation of the ICAO Legal Committee at its 33rd session, the ICAO Council decided that, as the rights of aircraft in designated air routes were not impinged upon, no amendment to Art. 2 Chicago Convention was necessary.

E. Significance

12 The evolution of ADIZs since World War II has been a natural outcome of the growth in capabilities of aircraft, especially their speed that materially reduces coastal State reaction time to perceived threats. The balance of interests now reflected in the rules governing the operation of ADIZs and interception of aircraft is likely to be maintained in the foreseeable future, except in those geographic areas where the political and defence interests of States with national airspace contiguous to international airspace are not in harmony, eg China and Taiwan (see also Straits, International).

13 In December 2007 China announced its intention to designate an ADIZ within the Taiwan Strait, and to begin a new air route on the Chinese side of, but close to, the median line. The authorities on Taiwan responded that this plan would undermine the stability in the strait and international aviation safety. Chinese authorities subsequently denied having such a plan.

14 Effective 10:00 am, 23 November 2013, China declared an ADIZ covering much of the East China Sea, overlapping the Taiwan, Japanese, and South Korean ADIZs and including the disputed Senkaku/Diaoyu Islands and the submerged rock Socotra/Ieodo claimed by South Korea and China. Accompanying the government statement announcing the ADIZ was the Ministry of National Defense (‘MND’) announcement of Aircraft Identification Rules for the East China Sea ADIZ. Unlike other ADIZ rules, the Chinese rules apply to all aircraft flying in the ADIZ, requiring them to report flight plans to the MFA or the Chinese Civil Aviation Administration and identify themselves to the MND. The rules also state that ‘China’s armed forces will adopt defensive emergency measures to respond to aircraft that do not cooperate in the identification or refuse to follow instructions.’ Unlike other ADIZ rules, the rules make no exception for aircraft not intending to enter Chinese national airspace. Further, unlike other ADIZs, the rules do not distinguish between civil and state aircraft. Japan, Korea, Australia, and the United States promptly protested these Chinese actions. While China is free to intercept aircraft in flight in its ADIZ, it must do so in accordance with the international procedures described above. Any threat or use of force against aircraft exercising their high seas freedom of overflight would be unlawful. On 23 and 26 November 2013, the United States publicly expressed its objections to China’s ADIZ along the foregoing lines (Digest of United States Practice in International Law 2013 372–73). On 28 November 2013 a spokesman for China’s People’s Liberation Army said the ADIZ was neither a no-fly zone nor territorial airspace and that it was incorrect to suggest China would shoot down planes within the zone. In response Japan and South Korea extended their ADIZs. The United States publicly repeated its concerns in February 2014 (Digest of United States Practice in International Law 2014 515–20).

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