East China Sea Air Defense Identification Zone

The East China Sea Air Defense Identification Zone (ECS ADIZ) was announced by China's Ministry of National Defense on 23 November 2013. Within the zone, aircraft are expected to file flight plans, maintain two-way radio contact, display clear nationality markings, and follow instructions from Chinese authorities, on pain of unspecified "defensive emergency measures."

An ADIZ is not the same as sovereign airspace. It is a unilaterally declared buffer in international airspace where a state asks foreign aircraft to identify themselves. The United States established the first ADIZ in 1950, and Japan, South Korea, Taiwan, and others operate their own. What made China's 2013 declaration controversial was less the concept than the geography and the rules.

The ECS ADIZ overlaps significantly with ADIZs already maintained by Japan, South Korea, and Taiwan. Critically, it covers the airspace above the Senkaku/Diaoyu Islands, administered by Japan but claimed by China and Taiwan, and the submerged Ieodo/Suyan Rock, disputed between China and South Korea. China also demanded compliance from all transiting aircraft, not merely those bound for Chinese airspace — a broader assertion than the US or Japanese practice.

Reactions were swift. Japan and South Korea rejected the zone. The United States flew two unarmed B-52 bombers through it on 26 November 2013 without notifying Beijing, and US carriers were initially advised not to comply, though the FAA later said US commercial airlines could file plans as a safety matter. South Korea expanded its own ADIZ (KADIZ) in December 2013 to overlap Ieodo.

Beijing has not formally declared a parallel South China Sea ADIZ, though officials and analysts have repeatedly speculated about one. The ECS ADIZ remains a frequent flashpoint, with Japan's Air Self-Defense Force scrambling regularly in response to Chinese and Russian aircraft operating in the zone.