The United States has one, Japan has one; so why is everyone so angry that China decided to have one its own? And why are its overseas supporters quiet for once? Simple. China’s Air Defense Identification Zone (ADIZ) is a one-of-a-kind device that extends sovereign authority over international airspace.
Specifically, the Chinese authorities are demanding that all aircraft that passes through its ADIZ must provide flight plan identification, radio identification, transponder identification, and logo identification to the Chinese Ministry of Foreign Affairs or Civil Aviation Administration. Moreover, such aircraft “should follow the instructions of the administrative organ of the East China Sea Air Defense Identification Zone or the unit authorized by the organ. China's armed forces will adopt defensive emergency measures to respond to aircraft that do not cooperate in the identification or refuse to follow the instructions.”
This is quite different from procedures adopted by the United States, which only “apply to aircraft bound for U.S. territorial airspace.” Sounds reasonable, doesn’t it? The United States accordingly “does not recognize the right of a coastal nation to apply its ADIZ procedures to foreign aircraft not intending to enter national airspace.” Also reasonable. Ergo the flyover by a pair of B-52 bombers, just to make the point. (The relevant paragraph is reproduced below.)
The Japanese ADIZ appears to amount to the same thing. Aircraft intending to enter Japan’s national airspace must report flight plans to the Ministry of Land, Infrastructure, Transport and Tourism (the civil aviation authorities), which is transmitted in real time to the Air Defense Force. Otherwise, the Japanese authorities impose no reporting requirements on aircraft passing through its ADIZ.
“184.108.40.206 Air Defense Identification Zones in International Airspace
"International law does not prohibit nations from establishing air defense identification zones (ADIZ) in the international airspace adjacent to their territorial airspace. The legal basis for ADIZ regulations is the right of a nation to establish reasonable conditions of entry into its territory. Accordingly, an aircraft approaching national airspace can be required to identify itself while in international airspace as a condition of entry approval. ADIZ regulations promulgated by the United States apply to aircraft bound for U.S. territorial airspace and require the filing of flight plans and periodic position reports. The United States does not recognize the right of a coastal nation to apply its ADIZ procedures to foreign aircraft not intending to enter national airspace nor does the United States apply its ADIZ procedures to foreign aircraft not intending to enter U.S. airspace. Accordingly, U.S. military aircraft not intending to enter national airspace should not identify themselves or otherwise comply with ADIZ procedures established by other nations, unless the United States has specifically agreed to do so."