US fighter jets have shot down four flying objects in nine days. Here is what we know so far.

Here is what we know so far:

What were the four objects?

Late last month, a giant Chinese balloon – termed a “spycraft” by US officials – drifted for days through US skies before being shot down on February 4 by an F-22 jet off the South Carolina coast.

China insisted the balloon was conducting weather research and had gone astray.

The Pentagon said it had a gondola the size of three buses and was equipped with multiple antennas, and had solar panels large enough to power several intelligence-gathering sensors.

It also appeared to be able to steer itself, using winds and possibly a propulsion mechanism, officials said.

• On February 10, US fighter jets downed another object off northern Alaska. It was much smaller than the previously shot-down balloon and lacked any system of propulsion or control, officials said.
• On February 11, a US F-22 jet shot down a “high-altitude airborne object” over Canada’s far northwest Yukon territory, saying it posed a threat to the civilian flight. Canada described it as cylindrical and about the size of a Volkswagen Beetle car.
• On February 12, President Joe Biden ordered US warplanes to down yet another unidentified object over Lake Huron. The object was described as an octagonal structure with strings hanging off it. It posed a hazard to civil aviation as it flew at about 20,000 feet (6,000 metres), officials said.

The Pentagon said none of the four objects appeared armed or posed any threat of attack.

Officials would not comment on the origin or function of the three objects that came after the Chinese balloon.

What has been recovered?

Military teams working from planes, boats and minisubs are scouring the shallow waters off South Carolina for debris from the balloon, with military images showing the recovery of a large piece.

Operations to recover the second object continue on sea ice near Deadhorse, Alaska. Recovery teams are searching for debris from the third object in the Yukon, while US and Canadian teams were preparing an operation to recover the fourth object’s debris.

Heino Klinck, former US deputy assistant secretary of defence for East Asia from 2019 to 2021, said there is concern about the lack of information about the flying objects over North America.

“It’s rather odd, frankly, that in a span of three days that the US air force shot down three objects in the air, and our government has yet to tell us anything about if there is a continuous threat or the origins of the aircraft,” Klinck told Al Jazeera.

What was the objects’ purpose?

US officials say the Chinese balloon, which flew over sensitive US nuclear missile sites, had surveillance equipment that could intercept telecommunications.

They said such balloons skirted US territory at least four times in the past six years, but none had flown deep into US territory.

The balloons were part of a “fleet” operated by China that has conducted surveillance on some 40 countries over five continents, US officials said.

Why so many objects now?

On Sunday, Melissa Dalton, assistant defence secretary for homeland defence, said after the Chinese balloon was detected, US air defence made adjustments to radar systems to be able to detect smaller and slower-moving objects in the atmosphere.

Analysts said normally, US and Canadian intelligence constantly receive huge amounts of raw data and generally screened some out to focus on the threat of incoming missiles, not slow-moving objects like balloons.

What’s the impact on US-China ties?

The US scrapped Secretary of State Antony Blinken’s China visit, intended to stabilise severely strained relations, and sanctioned six Chinese entities believed to support military spy balloon programmes.

Beijing denounced the first balloon’s downing, saying it “seriously violated international practice”. It reserved the right “to use necessary means to deal with similar situations”.

Dalton said on Sunday that after Beijing rejected US overtures for several days, US officials have had “contacts” with China over the balloon.