In an era of orbital satellites so advanced that they are able to make out objects half the size of cars from space, a spy balloon might seem like a bit of a relic.

They were a prominent tool for reconnaissance during the Cold War and were even used in a more basic form for intelligence gathering in the Napoleonic Wars more than 200 years ago.

But security experts say the balloons are just the “tip of a revolution” in the development and use of new high-altitude surveillance craft, with the UK even investing millions in a project to develop spy balloons last year.

It comes as the US military on Friday said it was tracking a suspected Chinese spy balloon, described as being the size of three buses, that has been flying over northwestern America in recent days.

Read more:
Chinese spy balloon flying over US airspace, says Pentagon
Spy balloon over US is actually a ‘civilian airship’, says China

A senior defence official said the US has “very high confidence” it is a Chinese high-altitude balloon and was flying over sensitive sites to collect information, while China has not immediately denied the balloon belonged to them.

Beijing admitted that the balloon had come from China, but insisted it was a “civilian airship” that had strayed into American airspace and that it was for meteorological and other scientific research.

US Secretary of State Antony Blinken is postponing a high-profile visit to China which had been due to begin on Sunday.

What are spy balloons?

The devices are lightweight balloons, filled with gas, usually helium, and attached to a piece of spying equipment such as a long-range camera.

They can be launched from the ground and are sent up into the air where they can reach heights of between 60,000ft (18,000m) and 150,000ft (45,000m), above the flight paths of commercial aircraft in an area known as “near space”.

Once in the air, they travel using a mixture of air currents and pressurised air pockets, which can act as a form of steering.

Why are they still useful in the satellite era?

According to defence and security analyst Professor Michael Clarke, the biggest advantage of spy balloons over satellites are that they can study an area over a longer period of time.

“The advantage is they can stay in one place for a long time,” he told Sky News.

“Because of the way the Earth rotates, unless a satellite is over the Equator, you need three to five satellites going all the time to track the same spot.

“These balloons are also relatively cheap, and much easier to launch than a satellite.”

Will balloons continue to be used in future for spying?

Very much so, according to Professor Clarke.

Despite the wide use of satellite technology, countries including the UK are also focusing on the development and use of spycraft to operate in the upper atmosphere.

In August, it was announced the Ministry of Defence had agreed a £100m deal with US defence company Sierra Nevada to provide high-altitude unmanned balloons to be used for surveillance and reconnaissance.

Professor Clarke said: “(These balloons) are the very tip of the revolution for passive upper atmosphere aircraft.”

He said other defence firms, such as BAE, were working on ultralight solar-powered drones which are able to operate in the upper atmosphere and stay in place for up to 20 months.

Why have China used them now?

According to Professor Clarke, the use of these balloons, if indeed they were launched by China, will likely have been a message to the US following its decision to open new military bases in the Philippines.

“I think it’s a challenge,” he said.

“They (China) are signalling that if the US is going to come closer to them then they will be more aggressive with their surveillance.

Watch: Future Wars: Could there ever be a conflict between the US and China?

“It is also caused a political issue in the US now, because it will be seen as a sign of weakness not to shoot it down.

“This causes some embarrassment, but the US doesn’t need to respond.”

The balloon was spotted over Billings, Montana, on Wednesday – close to one of the US’s three nuclear missile silo fields at Malmstrom Air Force Base.

Military and defence leaders said they considered shooting the balloon out of the sky but decided against it due to the safety risk from falling debris.

Professor Clarke added: “I think the debris issue is a bit of an excuse. It was over one of the least densely populated areas of the US and if they needed to they could have asked everyone to stay inside.

“I don’t think they wanted to make it a bigger issue, because China are daring them to shoot it down and make it an international issue.”

US secretary of state Antony Blinken has spoken with a senior Chinese official about his postponed trip to the country.

US officials said Mr Blinken spoke to the Director of the Central Foreign Affairs Office Wang Yi today postponing the planned visit.

But the secretary of state “indicated he would plan to travel” to China “at the earliest opportunity when conditions allow”.

Officials also said they “noted” China’s statement of regret but said “the presence of this balloon in our airspace is a clear violation of our sovereignty, as well as international law, and it is unacceptable that this has occurred”.

The diplomatic wrangling comes after a Chinese surveillance balloon has been tracked by US intelligence in recent days.

In a press conference today, the US defence department has said the Chinese spy balloon is heading eastwards but poses “no physical or military threat” to civilians.

The Pentagon’s press secretary would not confirm the current location of the balloon, which is operating at around 60,000ft.

There is also no evidence of any nuclear or radioactive material on board but it has the ability to be manoeuvred, according to Brigadier General Pat Ryder.

Watch:
Future Wars: Could there ever be a conflict between the US and China?

He also rejected Chinese claims that the balloon was in fact a “civilian airship” that had strayed into American airspace.

The US authorities said it now knows the object – spotted over Billings, Montana, on Wednesday, close to one of the US’s three nuclear missile silo fields at Malmstrom Air Force Base – was a Chinese balloon flying over sensitive sites to collect information.

US Secretary of State Antony Blinken postponed a high-profile visit to China which had been due to begin on Sunday.

Senior state department officials described the incident as a “clear violation of US sovereignty and international law” and said conditions were “not right at this moment” for Mr Blinken to travel.

Mr Blinken was prepared to depart for China tonight before the trip was postponed, Sky News understands.

He plans to travel “when conditions allow”, according to officials.

The Foreign Ministry in Beijing admitted the balloon had come from China – but said it was for meteorological and other scientific research.

The Pentagon spokesperson said it is “monitoring the situation closely and will continue to review options”.

Read more:
What are spy balloons?

The balloon will probably remain over the US for a few days, the spokesperson added.

US officials also confirmed military intelligence had previously seen similar surveillance balloons elsewhere.

The object is believed to have flown over the Aleutian Islands, off the coast of Alaska, and through Canada before entering the US.

Military and defence leaders had considered shooting the balloon out of the sky but decided against it due to the safety risk from falling debris.

US defence secretary Lloyd Austin convened a meeting of senior military and defence leaders to review the threat profile of the balloon and possible responses, which were presented to US President Joe Biden on Wednesday.

President Biden, speaking at a White House conference about jobs earlier today, refused to answer questions on the topic.

The US has engaged Chinese officials “with urgency” and communicated the seriousness of the situation.

China and the US have experienced tensions of late, clashing over Taiwan and China’s human rights record and its military activity in the South China Sea.

In an era of orbital satellites so advanced that they are able to make out objects half the size of cars from space, a spy balloon might seem like a bit of a relic.

They were a prominent tool for reconnaissance during the Cold War and were even used in a more basic form for intelligence gathering in the Napoleonic Wars more than 200 years ago.

But security experts say the balloons are just the “tip of a revolution” in the development and use of new high-altitude surveillance craft, with the UK even investing millions in a project to develop spy balloons last year.

It comes as the US military on Friday said it was tracking a suspected Chinese spy balloon that has been flying over northwestern America in recent days.

Read more:
Chinese spy balloon flying over US airspace, says Pentagon
Spy balloon over US is actually a ‘civilian airship’, says China

A senior defence official said the US has “very high confidence” it is a Chinese high-altitude balloon and was flying over sensitive sites to collect information, while China has not immediately denied the balloon belonged to them.

Beijing admitted that the balloon had come from China, but insisted it was a “civilian airship” that had strayed into American airspace and that it was for meteorological and other scientific research.

What are spy balloons?

The devices are lightweight balloons, filled with gas, usually helium, and attached to a piece of spying equipment such as a long-range camera.

They can be launched from the ground and are sent up into the air where they can reach heights of between 60,000ft (18,000m) and 150,000ft (45,000m), above the flight paths of commercial aircraft in an area known as “near space”.

Once in the air, they travel using a mixture of air currents and pressurised air pockets, which can act as a form of steering.

Why are they still useful in the satellite era?

According to defence and security analyst Professor Michael Clarke, the biggest advantage of spy balloons over satellites are that they can study an area over a longer period of time.

“The advantage is they can stay in one place for a long time,” he told Sky News.

“Because of the way the Earth rotates, unless a satellite is over the Equator, you need three to five satellites going all the time to track the same spot.

“These balloons are also relatively cheap, and much easier to launch than a satellite.”

Will balloons continue to be used in future for spying?

Very much so, according to Professor Clarke.

Despite the wide use of satellite technology, countries including the UK are also focusing on the development and use of spycraft to operate in the upper atmosphere.

In August, it was announced the Ministry of Defence had agreed a £100m deal with US defence company Sierra Nevada to provide high-altitude unmanned balloons to be used for surveillance and reconnaissance.

Professor Clarke said: “(These balloons) are the very tip of the revolution for passive upper atmosphere aircraft.”

He said other defence firms, such as BAE, were working on ultralight solar-powered drones which are able to operate in the upper atmosphere and stay in place for up to 20 months.

Why have China used them now?

According to Professor Clarke, the use of these balloons, if indeed they were launched by China, will likely have been a message to the US following its decision to open new military bases in the Philippines.

“I think it’s a challenge,” he said.

“They (China) are signalling that if the US is going to come closer to them then they will be more aggressive with their surveillance.

Watch: Future Wars: Could there ever be a conflict between the US and China?

“It is also caused a political issue in the US now, because it will be seen as a sign of weakness not to shoot it down.

“This causes some embarrassment, but the US doesn’t need to respond.”

The balloon was spotted over Billings, Montana, on Wednesday – close to one of the US’s three nuclear missile silo fields at Malmstrom Air Force Base.

Military and defence leaders said they considered shooting the balloon out of the sky but decided against it due to the safety risk from falling debris.

Professor Clarke added: “I think the debris issue is a bit of an excuse. It was over one of the least densely populated areas of the US and if they needed to they could have asked everyone to stay inside.

“I don’t think they wanted to make it a bigger issue, because China are daring them to shoot it down and make it an international issue.”