On 23 November 2013, China's Ministry of National Defense announced an Air Defense Identification Zone (ADIZ) over a large portion of the East China Sea. Aircraft transiting the zone are required by Beijing to file flight plans, maintain two-way radio contact, display clear identification, and follow instructions from Chinese authorities, with unspecified "defensive emergency measures" threatened for non-compliance.
An ADIZ is not a sovereign airspace claim under international law; rather, it is a unilaterally declared area in which a state asserts the right to identify civil aircraft for national security purposes. The United States pioneered the concept in 1950. What made the Chinese zone controversial was its geographic scope and enforcement language:
- It overlaps ADIZs previously declared by Japan, South Korea, and Taiwan.
- It covers the Senkaku/Diaoyu Islands, administered by Japan but claimed by China and Taiwan.
- It encompasses the submerged feature Ieodo/Suyan Rock, claimed by South Korea.
- Unlike most ADIZs, China's rules appear to apply to aircraft merely transiting the zone, not only those intending to enter national airspace.
Reactions were swift. On 26 November 2013, the United States flew two B-52 bombers through the zone without notifying Beijing. Japan and South Korea instructed their civil carriers not to comply with Chinese filing requirements, although several airlines elsewhere did. South Korea expanded its own KADIZ in December 2013 to overlap the Chinese zone over Ieodo.
The declaration is widely read as part of a broader Chinese effort to normalize administrative presence around the Senkaku/Diaoyu Islands following Japan's 2012 nationalization of three of the islets. Speculation that China would declare a similar South China Sea ADIZ has persisted but, as of writing, no such formal declaration has been made.
The zone remains a recurring flashpoint in US-China, Japan-China, and cross-Strait air encounters, and is frequently cited in debates over freedom of overflight and the management of overlapping maritime and aerial claims.
Example
In November 2013, days after China declared its East China Sea ADIZ, the United States flew two unarmed B-52 bombers through the zone without notifying Beijing, signaling non-recognition of the new identification requirements.
Frequently asked questions
No. Sovereign airspace extends 12 nautical miles from a state's coast under customary international law. An ADIZ is a unilaterally declared identification zone that can extend well beyond sovereign airspace and has no specific basis in a multilateral treaty.
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