Air Defense Identification Zone

An Air Defense Identification Zone (ADIZ) is airspace over land or water in which the identification, location, and control of civil aircraft is performed in the interest of national security. They may extend beyond a country's territory to give the country more time to respond to possibly hostile aircraft. The concept of an ADIZ is not defined in any international treaty and is not regulated by any international body.

The first ADIZ was established by the United States on December 27, 1950, shortly after President Truman had proclaimed a national emergency during the Korean War. Following the September 11 attacks in 2001, when civilian commercial aircraft were utilized for mass destruction, ADIZ became prominent as a tool by which to monitor and control foreign aircraft entering a given national airspace. About 20 countries and regions now have such zones including Canada, India,Japan, Pakistan, Norway and the United Kingdom, People's Republic of China, South Korea, Taiwan, United States, Sweden, Iceland and more. Russia and North Korea have unofficial ADIZ for themselves as well. Usually such zones only cover undisputed territory, do not apply to foreign aircraft not intending to enter territorial airspace, and do not overlap.

Air defense zones should not be confused with Flight Information Regions (FIRs), which are used to manage air traffic.

The United States maintains four zones: The Contiguous U.S. ADIZ; Alaska ADIZ; Guam ADIZ; and Hawaii ADIZ. Under U.S. law and policy, the zone applies only to commercial aircraft intending to enter U.S. airspace. An air defense command and control structure was developed in 1950, creating five Air Defense Identification Zones around North America. If radio interrogation failed to identify an aircraft in the ADIZ, the Air Force launched interceptor aircraft to identify the intruder visually. The air defense system reached its peak in 1962, however with the deployment of the SS-6 ICBM in the USSR, strategic threats shifted overwhelmingly to ICBM attacks, and bomber intrusions were considered to be less of a threat. It does apply to aircraft passing through the zone to other countries.

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