Words by ITV News Multimedia Producer Connor Parker
In fact, so little is known about them that when General Glen VanHerck, the head of US Northern Command, was asked if the objects could be extra terrestrials he said: "I haven’t ruled out anything at this point."
With the internet abuzz with speculation about aliens arriving in the US, many analysts are turning their eyes to China as the real culprit.
US officials firmed up their words on Monday. When speaking to journalists, press secretary Karine Jean-Pierre said there had been "no indication of aliens."
The first aircraft shot down was labelled by the Pentagon as a Chinese surveillance balloon, and many are guessing the latest objects are similar, but it is not the clear cut.
What happened with the first balloon?
On January 28 the US became aware of a large balloon floating over the country, high above normal flight levels.
The Pentagon quickly identified it as a Chinese surveillance balloon which sparked a diplomatic incident between the two countries.
As a result, US Secretary of State Antony Blinken cancelled a trip to China which was aimed at cooling tensions between the two countries.
Instead, relations deteriorated further as the US shot down the balloon after it drifted over the coast on February 4.
The balloon was recovered a few days later and handed over to the FBI for analysis.
On February 3 the US Department of Defence said it had detected another Chinese balloon floating over South America.
The balloon puzzled analysts and the Pentagon who pointed out that any information a spy balloon could have acquired, could have also been gained by a much harder to detect satellite.
On February 9 the US declassified intelligence on balloons that said a fleet of Chinese balloons had floated over more than forty countries.
It also said there were four previous times a balloon had been detected over the US.
The US said the previous incidents had either been detected too late or they had been unsure what it was to take action, but said improved detection systems gave them the information they needed to destroy it this time round.
What's happened with the other three aircraft?
Since the balloon was shot down on February 4 three more aircraft have been destroyed by the US airforce.
The first on February 10 was shot down over Alaska, the second on February 11 was shot down over Canada (with Canadian permission) and the third was destroyed on February 12 over Lake Huron in Michigan.
The first was flying at 40,000 feet, much lower than the original balloon destroyed the previous week, and within range of civilian aircraft.
John Kirby, White House National Security Council spokesman, said the object was about the size of a car, which was smaller than the Chinese balloon that was described as the size of three school buses.
All three were smaller than the first balloon and flying at much lower altitudes.
Pentagon officials said they were still trying to determine what exactly the three objects were and said they had considered using the jets’ guns instead of missiles, but it proved to be too difficult.
"We're calling them objects, not balloons, for a reason," said Gen VanHerck.
The US believe that due to the remote locations that the objects were found in, it is unlikely they are part of a Chinese spy balloon program.
ITV News' US Correspondent Dan Rivers spoke separately to a number of senators after a classified briefing who said the balloons were 'not very high of their worry chart'
Though President Joe Biden's administration does not yet have evidence that they were equipped for spying purposes, officials have not ruled that out either, Mr Kirby added.
He said it wasn't yet known who owned the object, and he did not say that they were balloons.
Officials also couldn't say if there was any surveillance equipment on it and didn't know where it came from or what its purpose was.
A similar story played out for the two subsequent shooting downs - airspace was closed, a US fighter was deployed and the object was destroyed.
Why is this happening now?
Although much of the recent incidents are surrounded in mystery, there is some information that can give us an idea as to why US fighters have been engaged over North America for the first time since the Second World War.
After the US shot down the first balloon and released the intelligence report on previous incidents they admitted there had been an "awareness gap."
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Since then the US has been adjusting its radar to find slow-moving flying objects.
They were previously attuned to finding fast-moving satellites, missiles and planes.US officials acknowledged even with the adjustments they are hard to find, even for the world's most sophisticated military.Gen VanHerck said: "What makes them really hard to detect and track is their size and potentially the shape," describing them as "very, very small objects that produce a very, very low radar cross-section."The revelation about these newfound objects floating over the US has led to the military going back and investigating all previous recent UFO sightings.
A report from the Office of the Director of National Intelligence issued last month cited 366 additional sightings, mostly things like balloons, drones, birds or airborne clutter. But 171 remained officially unexplained.
Still, Ronald Moultrie, undersecretary of defence for intelligence and security, told reporters in December that he had not seen anything in the files to indicate intelligent alien life.