An ADIZ, according the U.S. , is an Air Defense Identification Zone. All aircraft entering this zone must identify themselves to the controlling authority. Usually this is the civilian Air Traffic Control facility monitoring the ADIZ; however, at times, it may be a military authority, especially under heightened alert status. If aircraft do not identify themselves, they can be considered hostile. Usually, this just means that someone is sent to have a look at them, since they may be in distress. During time of war or national emergency, that someone is more likely to be a military interceptor.