(The Hill) — Three more objects were shot down by the U.S. military over the weekend after officials said they posed a threat to civilian airspace. 

The remarkable development came roughly one week after the U.S. shot down a Chinese surveillance balloon off the coast of South Carolina days after it was first reported to be hovering over the continental United States.

President Biden and Canadian Prime Minister Justin Trudeau on Saturday authorized the mission, and Biden ordered the U.S. military to send an F-22 fighter jet to take the object down in Canadian territory.

While U.S. officials have disclosed some information about the latest objects taken out of the sky, there are still major gaps in what even the government has learned about them and communicated publicly. 

Here is what is known about the objects shot down over the weekend, and what is still unknown.

Known

Friday over Alaska

The U.S. military took down an object off of the northern coast of Alaska on Friday afternoon. 

The “high-altitude object” was over Alaska at 40,000 feet and it was shot down at Biden’s direction on Friday afternoon, national security spokesman John Kirby confirmed at a press briefing that day. 

The object, which was described as much smaller than the Chinese spy balloon, landed in U.S. waters after a F-22 fired an AIM-9X Sidewinder missile to take it down. Officials have not said where the object originated from.

Saturday over Canada

The military on Saturday then shot down an unidentified, cylindrical object over frozen territory in northern Canada. 

Trudeau on Saturday authorized the mission and Biden ordered the U.S. military to send a F-22 fighter jet to take the object down in Canadian territory.

Officials said this object also did not resemble the Chinese spy balloon and avoided calling it a balloon. However, a Canadian defense official on Saturday did refer to it as a balloon, saying the instructions were that “whoever had the first, best shot to take out the balloon had the go-ahead.”

Sunday over Lake Huron

On Sunday afternoon, the military shot down an unidentified aircraft over Lake Huron, which stretches from Michigan to Ontario, Canada. 

The object was first detected over Montana on Saturday and was shot down with a F-16 fighter jet.

The Federal Aviation Administration briefly closed some airspace over Lake Michigan earlier on Sunday “to support Department of Defense activities,” the agency said in a statement to The Hill. The airspace has since been reopened.

Unknown

Where are these coming from and who is responsible? 

Some of the most basic information about the objects shot down over the weekend is still unknown, including who was operating them and what their purpose was.

Part of the issue is that officials have not been able to recover the debris yet from the objects shot down in recent days.

“We are going to continue to share as much information with the American people as we learn more about these objects,” Kirby said on MSNBC’s “Morning Joe” on Monday. 

“The truth is that we haven’t been able to gain access to the three that were shot down Friday, Saturday and yesterday, in large part because of the weather conditions, and the third one yesterday was shot down over Lake Huron, so it’s underwater.”

Glen VanHerck, the commander of the Pentagon’s Northern Command, made waves on Sunday when he was asked if officials had ruled out the possibility that the objects were connected to extraterrestrials.

“I’ll let the intel community and the counterintelligence community figure that out. I haven’t ruled out anything at this point,” VanHerck said.

Are objects flying in our skies a new phenomenon? 

It does not appear that balloons or other objects entering U.S. airspace is a brand new development, though the response of shooting them down has been.

A Pentagon official told reporters after the first surveillance balloon was shot down on Feb. 4 that Chinese spy balloons had transited U.S. airspace “at least three times during the prior administration and once that we know of at the beginning of this administration, but never for this duration of time.”

Former senior Trump administration officials have said they were unaware of the objects while they were in office, raising questions about whether they previously went undetected or if spottings were not communicated up the chain of command for some reason. 

Officials said on Saturday that because of the Chinese spy balloon shot down last week, “we have been more closely scrutinizing our air space at these altitudes, including enhancing our radar, which may at least partly explain the increase in objects that we’ve detected over the past week.”

Lawmakers over the last week have been raising questions over why this is the first time they are learning about balloons or other objects over U.S. airspace.  

“I think our military, our intelligence is doing a great job, present and future,” Senate Majority Leader Charles Schumer (D-N.Y.) told ABC News. “I feel a lot of confidence in what they are doing. But why as far back as the Trump administration, did no one know about this?”

Does the US fly objects over other countries?

China on Monday claimed more than 10 U.S.-controlled balloons flew into Chinese airspace in the last year, an assertion White House officials forcefully rejected.

A Chinese foreign ministry spokesperson did not provide any details about the incursions or how China responded.

Kirby on Monday said China’s claim was “absolutely not true.”

Adrienne Watson, a spokeswoman for the White House National Security Council, called it “the latest example of China scrambling to do damage control.” 

“It has repeatedly and wrongly claimed the surveillance balloon it sent over the US was a weather balloon and has failed to offer any credible explanations for its intrusion into our airspace, airspace of others,” Watson tweeted.

How much of a threat is it?  

It’s unclear if the three objects shot down over the weekend had a connection to China or the Chinese surveillance balloon from a week prior.

In the case of Friday’s object, Kirby said it posed a reasonable threat to civilian flight. 

He acknowledged on Monday that the objects may be “completely benign,” and that they could belong to tech companies or research institutions.

The objects shot down on Saturday and Sunday also raised a threat to civilian aircraft, officials have said, but officials haven’t pointed to immediate military threats.

Rep. Mike Turner (R-Ohio), the chairman of the House Intelligence Committee, said that there is an inherent threat considering there are multiple objects being shot down.

“What I think this shows, which is probably more important to our policy discussion here, is that we really have to declare that we’re going to defend our airspace. And then we need to invest,” he said on CNN.