An Air Defense Identification Zone (ADIZ) is a designated airspace area where aircraft are required to identify themselves and follow specific procedures to ensure air defense and national security. The main purpose of an ADIZ is to provide early warning and identification of aircraft approaching or entering a country's airspace, allowing air defense systems to respond quickly and effectively to potential threats.

Here are some key aspects of an ADIZ:

1. Notification and identification: Aircraft entering an ADIZ are typically required to contact air traffic control and provide their identification, flight plan, and other relevant information.
2. Flight plan filing: Aircraft must file a flight plan with air traffic control before entering the ADIZ, which includes details such as route, altitude, and estimated time of entry.
3. Transponder requirements: Aircraft may be required to operate their transponders, which transmit their identity, altitude, and position to air traffic control and air defense systems.
4. Communication protocols: Pilots must follow specific communication protocols, such as contacting air traffic control on designated frequencies and using standardized phraseology.
5. Air defense response: If an aircraft fails to identify itself or follow procedures, air defense systems may respond with measures such as intercepts, warnings, or even military action, depending on the perceived threat level.

ADIZs are typically established by countries to protect their airspace and national security interests. They can be particularly important for countries with sensitive or strategic locations, such as near borders, military bases, or major cities.

Examples of ADIZs include:

• The North American Aerospace Defense Command (NORAD) ADIZ, which covers the airspace of the United States and Canada
• The East China Sea ADIZ, established by China in 2013 to assert its claims over disputed territories
• The Korean Air Defense Identification Zone (KADIZ), which covers the airspace around the Korean Peninsula

It's worth noting that ADIZs are not the same as airspace boundaries or borders, and they do not necessarily imply sovereignty or territorial claims. However, they can be a source of tension and conflict between countries, particularly if their boundaries overlap or are disputed.