How does the U.S. monitor airspace violations?

The North American Aerospace Defense Command (NORAD) identifies potential airborne threats to the United States and Canada through a network of radars and sensors. In early February it tracked a high-altitude balloon flying over the continental United States that the Pentagon identified as a Chinese surveillance mission. A U.S. fighter jet shot down the balloon on Feb. 4 after it floated out over Atlantic waters. On Feb. 10, U.S. fighter jets shot down a second slow-moving, “high-altitude object” near the north coast of Alaska. The U.S. military has admitted it failed to detect several previous balloon incursions. Here’s more about NORAD:

What does NORAD do once it identifies a flying object approaching North America? If the object appears to be a threat, defense officials might launch a fighter jet to intercept and escort an approaching aircraft away from the coast—or shoot it down, if necessary. Ground-based missiles can also do the job.

Did China ignore international rules when its balloon entered U.S. airspace? Yes, though defense officials did not immediately shoot it down because they did not consider it an imminent threat. Nations can establish reasonable conditions for aircraft to enter their airspace and often do this by establishing buffers called air defense identification zones. ADIZs can be in international airspace adjacent to sovereign airspace, and the U.S. and Canadian ADIZ extends up to 200 miles from the coast—well beyond the 12-mile sovereign airspace recognized in UN and international civil aviation conventions. Any civilian aircraft wanting to enter U.S. or Canadian airspace must file a flight path at least one hour prior to entering the ADIZ. The same reporting requirements are generally not applied to military aircraft, but the Chinese government claimed its balloon was a civilian craft.

Are ADIZ violations routine? Russian military aircraft often enter the Alaskan and Canadian ADIZ without permission, most recently in October 2022. When that happens, U.S. aircraft respond and escort the aircraft through the zone in a cat-and-mouse routine. Approximately 20 nations have established ADIZs in international airspace.

What precautions did the U.S. military take while China’s balloon was above the country? The commander of the U.S. Northern Command and NORAD, Gen. Glen VanHerck, said the military “took maximum precaution to prevent any intel collection.” He also said military officials sent messages to units across the Defense Department to take “maximum protective measures while the balloon transited across the United States.” Those measures likely included ­moving equipment or weapons that were under the balloon’s flight path or modifying activities such as troop or weapons movements and maintenance of sensitive aircraft or equipment outdoors. The U.S. military also may have limited electronic communications that could be intercepted by the equipment on the balloon. The military regularly takes precautions to limit observations from satellites or when Chinese or Russians operate close to U.S. military activities.

WORLD updated this story on Feb. 10.