An air defense identification zone, or ADIZ, is airspace often set over territorial land and waters for national security reasons. But it extends far beyond a country’s airspace so that there is more time to respond to foreign and possibly hostile aircraft. The establishment of such a zone is to facilitate the location, surveillance, and control of aircraft by the military.
There are no international treaties or agreements governing the air defense identification zones, so countries may impose different rules in their zones.
The first air defense identification zones were set up by the United States. In the late 1950s, in response to what it saw as rising threats from Soviet bombers, the US worked with Canada to create five such zones.
Now over 20 countries maintain air defense identification zones, including Japan, China, South Korea, Taiwan, and India.
The air defense identification zone should not be confused with the flight information region. The division of flight information regions is conducted through the International Civil Aviation Organization (ICAO). A country’s flight information region generally covers the country’s airspace and the surrounding high seas.