What just happened? In a situation thought to be unprecedented in peaceful times, the US military has shot down a fourth flying object over North American airspace this month. The latest target, described as an octagonal structure with strings but no payload, was shot over Lake Huron in Michigan at 2.42 pm local time on Sunday following orders from President Biden.

A Pentagon statement said the object was detected traveling at 20,000 feet above military sites in Montana on Saturday, an altitude that could have caused it to interfere with commercial air traffic. F-16 fighter jets used an air-to-air missile to down the object as it traveled across the Great Lake region.

The incident marks the fourth of its kind in eight days. On February 4, a large balloon suspected to be used for surveillance was shot down off the coast of South Carolina. China said it belonged to the country but insisted the balloon was blown off course while carrying out weather research, though the Pentagon says the equipment it carried could have been used to intercept communications.

The objects shot down in Alaska and Yukon, Canada, were much smaller than and did not closely resemble the first balloon. The military has been on heightened alert and looking for UFOs on radar since the initial sighting.

As per the BBC, a defence official said the US had communicated with Beijing about the first object after receiving no response for several days.

US Air Force Gen Glen VanHerck, head of NORAD and US Northern Command, said the military had not identified what the three most recent objects were or how they stayed afloat. He told reporters they were being referred to as "objects, not balloons, for a reason."

Talk of unidentified flying objects has led to questions about extraterrestrials. When asked if such a scenario had been ruled out, VanHerck said, "I'll let the intel community and the counterintelligence community figure that out. I haven't ruled out anything." However, an anonymous defense official told Reuters that there had been no evidence suggesting the objects were extraterrestrial, and one senior official told ABC News that the three most recent objects were likely weather balloons rather than surveillance balloons.

The US and Canada are currently in the process of recovering debris from the downed objects for analysis. Some debris from the first balloon has already been recovered.

"What's gone on the last two weeks or so [...] has been nothing short of craziness. And the military needs to have a plan to not only determine what's out there, but determine the dangers," said Jon Tester, the senior senator from Montana.

The incidents have caused tensions between the US and China to reach heights not seen since Nancy Pelosi visited Taiwan last year. Bloomberg writes that China is preparing to take down an unidentified object flying over waters near the port city of Qingdao, about 15 miles east of Jianggezhuang Naval Base, home to ballistic and nuclear attack submarines and the country's first aircraft carrier. "China reserves the right to use necessary means to deal with similar situations," China's Defense Ministry spokesperson Tan Kefei said after the first object was shot down in the US.