The US has begun recovering debris from a Chinese "surveillance" balloon shot down off the coast of South Carolina on Saturday — but there is still much to be learnt about the balloon and its purpose.
Gen Glen VanHerck, commander of the North American Aerospace Defence Command, said on Monday that the vessel was 60 metres wide and the same distance tall, with a payload underneath weighing more than 900 kilograms.
“They utilised their manoeuvrability to strategically position themselves to utilise the winds to traverse portions of countries that they want to see,” Gen VanHerck said, referring to China.
"But this gave us the opportunity to assess what they were actually doing, what kind of capabilities existed on the balloon, what kind of transmission capabilities existed.”
He did not rule out that there could have been explosives on the balloon, but said he did not have any evidence of it. That risk, however, was a factor in his planning to shoot down the balloon over open water.
President Joe Biden said he gave the order to shoot down the balloon on February 1 when it was seen over Montana, but the Pentagon advised him doing so could threaten property and lives on the ground.
The balloon fell about 9 kilometres off the South Carolina coast in about 14 metres of water, the Pentagon said.
China has claimed that the airship was a civilian balloon that was being used for meteorology research when it veered off course.
White House National Security Council spokesman John Kirby confirmed that propellers and steering mechanisms gave the vessel some semblance of control, not typical of weather balloons.
"It is true that this balloon had the ability manoeuvre itself — to speed up, to slow down and to turn," Mr Kirby said.
"So it had propellers, it had a rudder, if you will, to allow it to change direction. But the most important navigational vector was the jet stream itself, the winds at such a high altitude."
Chinese Vice Foreign Minister Xie Feng said he lodged a formal complaint with the US embassy on Sunday over the “US attack on a Chinese civilian unmanned airship by military force".
Mr Kirby said that, waiting to shoot it down and having the time to study its functions, and soon retrieving its parts, would help the US to gain better understanding of China's surveillance balloon operations.
Members of the public were warned to not touch any debris that washed ashore.
“Debris should not be touched, moved or removed. Such items are part of a federal investigation and tampering could interfere in that investigation,” the Sunset Beach, South Carolina police department said.
The incident is the latest to have strained relations between the two superpowers, prompting Secretary of State Antony Blinken to postpone his long-planned trip to Beijing.
His "visit was postponed, it wasn't cancelled, and — as Secretary Blinken has said himself — when the time is right, he will begin discussing with the Chinese what a future visit could look like", Mr Kirby said.
Mr Blinken would have been the highest-ranked US official to visit China since the Covid-19 pandemic.
"It just wasn't the appropriate thing for Secretary Blinken to do to visit Beijing in light of this egregious violation of our sovereign airspace," Mr Kirby said.
Pentagon officials said the balloon entered US airspace on January 28 when it passed over Alaska.
US Senate majority leader Chuck Schumer said all members of the upper house would be briefed on the suspected spy balloon on February 15.
A second Chinese balloon was seen over Latin America.
Chinese Foreign Ministry spokeswoman Mao Ning said the balloon was an unmanned civilian airship that inadvertently entered the area because it was “affected by the weather and because it has limited self-steering capability”.
China says balloon flying over Latin America was for civilian use
Agencies contributed to this report