Bizarrely, the Chinese have sent a high-flying spy balloon deep into the American heartland. The logic is that such balloons fly more than 22.2 kilometres above the surface. Under international law, a nation’s territorial seas and the airspace above it extend to 12 nautical miles (22.2km). Accordingly, China’s high-altitude balloons are arguably flying in international airspace. It’s plausibly legal but also highlights the fact that if a balloon overflies a country below 22.2 kilometres altitude, that country’s sovereignty has been infringed and the craft can be legally shot down. Both happened in this case over the weekend.

High-flying balloons are very common. Some 800 small weather balloons are launched daily and fly up to 40 kilometres altitude. The United States launched hundreds of spy balloons over the Soviet Union in the 1950s. The Soviets grumbled that these were “incompatible with normal relations between states”, and they had a point. Some 90 per cent failed, and then came the development of spy satellites that were more capable, reliable and less provocative. Using balloons for long-range spy missions went out of fashion.

Please click here to read the full “Chinese grey zone spy balloons over the American heartland” article published at The Interpreter, written by Griffith Asia Institute Visiting Fellow, Dr Peter Layton.