In 1950, the United States became the first country in the world to declare the establishment of an air defense area. Although there have been a number of countries since then, they have declared the establishment of an air defense area, but there is no clear regulation in international law that regulates this issue. The paper clarifies three issues: 1. The legal regime for international airspace and international airspace is related to civil aviation activities in the national airspace and international airspace as stipulated in the articles International treaties and related documents of the International Civil Aviation Organization. 2. Evaluate the impacts of the air defense identification area on civil aviation activities of aircraft as well as the management activities of the relevant civil and international civil aviation organizations. 3. Evaluate China's ability to establish an air defense identification area in the East Sea and some suggestions for Vietnam.