Borders stand out on maps. Lines get hazy farther above.

Borders stand out on maps. Lines get hazy farther above.

 Several of the more than 5,000 satellites circling the Earth can produce high-resolution photos. Foreign treaties are not as clear.

By looking at a map, it is easy to see where a boundary begins and ends. Just how far into the sky does that line extend?

The downing of a Chinese balloon by the US Navy off the coast of South Carolina in February 2023 has raised fresh concerns about the sky.

The balloon was monitored as it traveled through the United States. The Chinese authorities claimed that the balloon was monitoring the weather, although its size – 200 feet (61 meters) tall — was far greater than regular weather balloons. The huge mass of the cargo, described as "the size of a regional passenger plane," sparked suspicions that the true objective was surveillance.

Airplanes have been around since 1903. Satellites first appeared in 1957. Yet, the legal definition of the top limit of sovereign or national territory has never been established.

Passenger planes fly at altitudes ranging from 35,000 to 40,000 feet, or around 11,000 to 2,000 kilometers. Military planes can fly at twice that altitude.!

Establishing sovereignty of airspace is not so simple.

Both passenger and military aircraft operate in accordance with the 1944 Chicago Convention. Because "any state has total and exclusive control over airspace above its territory," aircraft must seek authorization to "engage in international navigation." Yet, the Agreement also specifies that States must provide a certain amount of access to civil aviation.

The Chicago Conference served as the foundation for the International Civil Aviation Organization (ICAO), which is today a United Nations body. Yet, ICAO standards do not address the vexing issue of the highest limit of sovereign airspace.

Satellites can orbit as low as 99 miles (160 km) and as high as 20,000 miles above sea level (32,000 km). Nonetheless, they are not regarded to be in violation of sovereign airspace.

This is not the case with airplanes.

Spies in the skies

The Soviet Union shot down an American jet over central Russia in 1960. It was a U-2, a cutting-edge spy jet meant to photograph strategic targets. The US claimed that the jet was performing weather observations, a claim quickly debunked by documents discovered in the plane's wreckage.

Gary Powers, an American pilot, was caught and imprisoned by the Soviet Union. Two years later, he was returned in exchange for a Soviet spy uncovered in the United States.

Nonetheless, some surveillance operations resulted in fatalities. In 1962, a U-2 aircraft was shot down over Cuba, and four times over China in the 1960s.

Although the U-2 is the most famous American espionage plane, other U.S. planes created.

Not all nations are open to Open Skies.

According to the treaty language, the Open Skies Treaty was established to encourage "more openness and transparency in their military actions" and to "improve security through confidence." Nonetheless, the members are entirely from North America and Europe.

The Open Skies Treaty has not been signed by China. But would a notion of sovereign airspace make a difference in terms of surveillance?

Several of the more than 5,000 satellites circling the Earth are capable of generating high-resolution photos with resolutions of up to 3-5 meters. Moreover, satellite data is not confined to governments.

Establishing sovereign airspace and space boundaries has not been a top concern for the international community. The lack of a defined upper limit on national airspace is advantageous to any party wishing to undertake intelligence operations from the air or space.