Chinese “Weather” Balloon: What Happened?

The use of balloons goes back thousands of years. But what are their history and can the US shoot down another country’s balloon?

View of the Chinese Balloon taken from the ground
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With recent news of a Chinese “weather” balloon traversing over the United States, and the revelation that there’s another one floating across Latin America I thought we’d take a look at the history of balloons, some interesting facts surrounding them and what the laws are about flying a balloon over another country’s air space.

A Brief History Of Balloons

The exact origins of balloons aren’t known but they can be traced back over 2000 years to the Han Dynasty in (ironically) China.

These were commonly referred to as “sky lanterns” or “wish lanterns”. Made from paper around a bamboo frame, the lift was provided by a small candle placed at the base of the paper casing. The candle heats the air contained in the paper which provides lift allowing the lantern to float into the air.

The tradition of lighting and releasing sky lanterns during festivals and celebrations has since spread to other parts of the world and it is quite common to see hundreds of these lanterns being released at once.

These lanterns are quite different from what we think of as a “proper” balloon. While a lantern is quite small and usually made of paper, a balloon tends to be made of durable materials such as nylon or polyester which contains the hot air that provides the lift.

The first hot air balloon was invented by the Montgolfier brothers, Joseph-Michel and Jacques-Étienne, in 1783. They discovered that by heating air in a bag, it would rise and become lighter than the surrounding air, causing the bag to float. This was the principle behind their invention of the hot air balloon.

The balloon (or envelope) of their first balloon was made from paper and fabric and the air was heated by burning straw and wool in a fire under the envelope – probably something that wouldn’t pass health and safety standards today!

Hundreds of sky lanterns being released against a black sky

Image Source: Rebecca Swafford on

How High Can A Balloon Go?

Balloons can reach a maximum altitude of approximately 20 miles (approximately 105,000 feet or 32 kilometres) above sea level, beyond which the atmospheric pressure is too low for them to maintain their shape. However, most balloons used for leisure, such as hot air balloons, typically fly at much lower altitudes, usually between 1,000 to 6,000 feet (300 to 1,800 meters), depending on weather conditions and the pilot’s discretion.

High-altitude balloons, such as weather balloons or scientific research balloons, can reach much higher altitudes, up to 120,000 feet (36,576 meters) because they are filled with hydrogen or helium which are lighter than air gases. This allows them to rise to much higher altitudes, sometimes even into the stratosphere, where they can collect data on atmospheric conditions.

In comparison, hot air balloons are filled with air that is heated by a burner, and they rely on the difference in density between the hot air inside the balloon and the colder air outside to generate lift. As a result, they are limited to much lower altitudes, typically a few thousand feet above the ground.

The Chinese Balloon spotted over the US in 2023 was flying at an estimated 60,000 feet (18km) so well within the tolerances of a high-altitude balloon.

Can You Steer Balloons?

Steering a weather balloon is challenging because they are carried by the wind currents and cannot be directly controlled. Weather balloons are usually equipped with a radio transmitter to send data back to the ground, but they have no propulsion system to change their direction.

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However, there are some ways to indirectly influence the balloon’s trajectory:

Launching The Balloon At A Specific Time And Location

The direction of the wind can be predicted, and the launch time and location can be adjusted to take advantage of favorable wind patterns.

Adjusting the balloon’s altitude

The wind direction and speed can change with altitude, so adjusting the altitude of the balloon can influence its trajectory.

Using multiple balloons

Launching multiple balloons at different times and locations can increase the chances of collecting data from a desired area.

Despite these methods, weather balloons are generally at the mercy of the wind and their trajectory is largely determined by the weather conditions at the time of launch.

The 2023 Chinese balloon was reported to have a rudder which would allow for some minimal steering but the majority of its travel would be down to where the air currents would take it.

How Big Are Weather Balloons?

Weather balloons, or sounding balloons, can vary in size depending on the specific requirements of the data-gathering mission. However, they are generally larger than normal hot air balloons and can reach sizes of up to several meters in diameter when fully inflated.

At launch, weather balloons are usually around 1 meter in diameter and filled with hydrogen or helium to a pressure that will allow them to expand as they rise through the atmosphere. As they rise, the balloons continue to expand, reaching maximum sizes of several meters in diameter before bursting at high altitude.

The size of a weather balloon is carefully controlled to ensure that it can carry the necessary instruments and sensors to collect data on atmospheric conditions, while still being able to reach the desired altitude before bursting.

The 2023 Chinese Balloon was around 90 feet (27 metres) in diameter meaning it is at least 4 times the size of a standard weather balloon.

Why Use A Balloon Instead Of A Satellite?

Balloons and satellites both have their advantages and disadvantages for different purposes.


Balloons are relatively cheap compared to satellites, making them a more cost-effective option for certain applications, such as atmospheric research or temporary telecommunications services.

Speed of Deployment

Balloons can be deployed much more quickly than satellites, which can take years to design, build, and launch.


Balloons can be deployed in remote or hard-to-reach locations, and their trajectory can be influenced by adjusting their altitude. Satellites, on the other hand, are limited to specific orbits and are much more difficult to reposition.

Limited Lifespan

Balloons have a limited lifespan and typically last for only a few days, whereas satellites can last for several years.

Data Collection

Balloons can carry a variety of instruments and equipment to collect data and transmit it back to the ground. They can also remain in a relatively static location by raising and lowering its altitude which enables higher resolution photos to be take over its satellite counterparts[1][ArsTechnica: Why would the Chinese government be flying a large stratospheric … Continue reading

In summary, while satellites offer a more persistent and reliable platform for certain applications, balloons offer a flexible and cost-effective solution for others. The choice between a balloon and a satellite depends on the specific requirements and goals of the mission.

When Was The First Recorded Spy Balloon?

The first recorded use of a balloon for military reconnaissance, or “spy balloon,” was during the American Civil War. In 1861, Union Army Major Thaddeus Lowe launched a hydrogen-filled balloon called the “Enterprise” to observe Confederate positions.

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This was one of the first documented uses of a balloon for military purposes, and it marked the beginning of the use of balloons for aerial reconnaissance.

Since then balloons have been used in almost every major conflict thanks to their ability to fly extremely high therefore avoiding detection, which was especially important before the invention of stealth technology.

Have Any Spy Balloons Crashed?

Yes, there have been instances of spy balloons crashing. Spy balloons, also known as reconnaissance balloons, have been used by military forces for aerial surveillance and intelligence gathering. However, like any aircraft, they are subject to technical malfunctions, weather conditions, and other factors that can cause them to crash.

There have also been instances of spy balloons being shot down or intentionally brought down by opposing forces during times of conflict. For example, during World War I, both the Allied and Central Powers used reconnaissance balloons to gather intelligence, and many of these balloons were shot down by enemy forces.

Overall, while spy balloons have proven to be useful tools for military reconnaissance, they are not without risk and have been involved in crashes and incidents over the years.

Have Spy Balloons Been Used Over America Before?

Yes! Spy balloons have been used over America in the past. During the Cold War, the United States and the Soviet Union both used spy balloons for aerial surveillance and intelligence gathering. The balloons were equipped with cameras, sensors, and other instruments to gather data and transmit it back to the ground.

More recently, in 2009, a number of military surveillance balloons were deployed by the US Department of Homeland Security along the Mexican border to monitor for illegal border crossings and other security threats.

Spy balloons have also been used for scientific research and environmental monitoring, as well as for providing telecommunications services in remote areas. The use of spy balloons continues to evolve, and they remain an important tool for various military, scientific, and commercial applications.

What Is The Importance Of The 2023 Chinese Spy Balloons?

The first main thing to note is the sheer size of the balloon. Not only was the envelope extremely large, the payload (the monitoring equipment hung underneath the envelope) was estimated to weigh round 2000lbs (910kg) – this is an important factor which we will cover later.

The balloon also had solar panels for powering the equipment on board although according to one source cited in the Wikipedia article on the incident ” National Security Council spokesman Admiral John Kirby said the craft had a propeller and could be maneuvered”.

Can The US Legally Shoot Down Balloons Over Their Airspace?

Yes. And No.

To allow for international air travel there are rules and regulations in place that allow one country to overfly another. This was ratified by all members of the U.N (excluding for some reason Lichtenstein) in the “Convention on International Civil Aviation”[2]ICAO Publication that went into effect in 1947.

Also known as the “Chicago Convention” the treaty essentially covers who can do what when it comes to flying in another country’s airspace. Article 3 of the Chicago convention states that a country must refrain from using weapons against another country’s civil aircraft when it is in flight.

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But that’s where the interesting bit is – “civil” aircraft.

So is a weather balloon a “civil” aircraft, in other words non-military? Yes, it is, if it meets certain criteria.

In the Chicago Convention, appendix four of Annex Two (titled “rules of the air“) discusses unmanned balloons and the rules and regulations surrounding them. As you cannot technically control a balloon regulations need to be laid out about what constitutes a balloon and what rights the operator and the country it’s overflying have.

Within Appendix 4 it states that the operating country should obtain permission from the country that the balloon will be flying over before the balloon is launched. These sections (2.2 and 2.3) relate to what are referred to as “unmanned free balloons” and do not apply to “light balloons” used “exclusively for meteorological purposes” which are exempt from needing permission due to their smaller size.

The Chinese were claiming that as this was a weather balloon it is therefore a “civil” aircraft and they do not need to see permission from the countries it was overflying. This would technically be true if the balloon fit into the category of a “light balloon” but this is where its size and weight come into play.

The Chicago Convention defines a “light balloon” as carrying a payload with a combined mass of less that 4kg. You’ll remember from earlier that the estimated payload weight of the Chinese balloon was 920kg – well above what would be considered a “light balloon” which would mean that under the Chicago convention they would have needed to obtain permission from the United States so that the balloon was legally allowed to enter their airspace.

And again, under the Chicago Convention the Chinese government would have needed to obtain permission before the balloon took flight.

Additionally when confirming that the balloon was in fact Chinese a Chinese government spokesperson stated that it was a “civilian airship used mainly for meteorological purposes.”[3]Aljazeera: China says balloon over US airspace is civilian airship

The key phrase here is “mainly”.

Within the Chicago Convention, notification rules only apply to balloons if they are used exclusively for meteorological purposes, not “mainly” meteorological purposes so yet again they would still be required to alert the United States that the balloon would be overflying their territory.

While the Convention on International Civil Aviation covers civilian aircraft (including balloons), the sheer size of it and the fact that it’s not just a weather balloon means that it isn’t covered under these rulings and the Unites States are well within their legal rights to defend their sovereign airspace.

Whether they should have looked to a more diplomatic means of solving the situation rather than blasting the balloon out of the sky remains to be seen.


1 [ArsTechnica: Why would the Chinese government be flying a large stratospheric balloon?](
2 ICAO Publication
3 Aljazeera: China says balloon over US airspace is civilian airship

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