AMNA NAWAZ: Now to the ongoing story of unidentified flying objects crossing into American and Canadian airspace.

Four, including a Chinese spy balloon, have been shot down over the last week.

National Security Council spokesperson John Kirby fielded dozens of questions about the matter today and specifically what's known about China's balloon program.

JOHN KIRBY, NSC Coordinator For Strategic Communications: We were able to determine that China has a high-altitude balloon program for intelligence collection that is connected to the People's Liberation Army.

It was operating during the previous administration, but they did not detect it.

We detected it.

We tracked it.

And we have been carefully studying it to learn as much as we can.

AMNA NAWAZ: For more on the detection and decisions to shoot down these objects and where they could be coming from, we turn to retired Major General Scott Clancy.

Formerly of the Canadian Air Force, his last assignment was director of operations at the North American Aerospace Defense Command, or NORAD.

General Clancy, welcome, and thanks for joining us.

John Kirby and other officials have said, we're seeing more of these objects, in part because we're looking more, right?

There have been some changes at NORAD in terms of ratcheting it up the defense detection there.

Explain to us what what's happened.

What's different at NORAD?

What are they seeing now they weren't before?

MAJ. GEN. SCOTT CLANCY (RET.

), Canadian Air Force: So, that's a great question.

General VanHerck alluded to it in his Pentagon briefing, the commander of NORAD, right after the shoot-down of the Chinese balloon, the very first object.

And what he said was, he had intelligence gaps that he has since closed.

And then, after the first shoot-down of these unidentified objects in Alaska, it was made clear that they have changed the filters on the radars.

And what that means is, is that when you have radar data that's coming in, it can be overwhelming to the operators of that, so that they will filter out those things that aren't pertinent to the threats that you're expecting.

So, for example, in this instance, it was probably, we're not going to look at targets or we don't want any radar information with air speeds below, let's say, 80 knots, which means that, because you're looking for aircraft and cruise missiles that go hundreds of miles an hour, then you wouldn't be looking at that.

Now they're seeing that data, and they're getting more track.

AMNA NAWAZ: So, one of the questions, of course, is that the first balloon or flying object was clearly they have identified as a Chinese spy balloon.

The questions around these last three objects and what they were -- and we spoke earlier with a man named Paul Fetkowitz.

He's actually head of the largest provider of weather balloons to the U.S. government, including to the military.

And he said, on any given day, there are some 300 balloons up in the air over the United States.

He thinks these last three objects that were shot down were likely government or privately funded research devices.

Take a listen to what he said.

PAUL FETKOWITZ, Kaymont Consolidated Industries: Now NORAD is picking up, potentially lighting up like a Christmas tree, because they're picking up all these funded research programs, the Southern Great Plains Research, the Department of Energy, the North Slope Project, all the artillery bases.

All the test ranges that we have here in the United States are launching balloons on a regular basis.

And all could potentially be picked up because these balloons go up to 100,000 feet, every one of them.

AMNA NAWAZ: General Clancy, could he be correct?

MAJ. GEN. SCOTT CLANCY: Sure.

He absolutely could be correct.

As General VanHerck alluded to, and I think that all the agencies in both nations are being very prudent with respect to attribution of what these things are, until they get some idea from the wreckages of exactly what they are.

Now, I will caution a little bit of concern here.

It could be these things.

That doesn't really ring true to me, however.

And here's the reason why.

In NORAD, all of -- not all of these research elements, but the vast majority of weather balloons that are launched are launching within the flight restrictions of the FAA.

We're saying that then, very quickly afterwards, they're going to come back down.

That's not how these balloons are set to operate.

And that's why they're not a threat to civil aviation.

These were persistent.

They were persistent through the airspace and had been tracked in some instances for multiple days.

That's more indicative of something that is an intelligence-gathering asset, and not just a weather balloon that's designed to go up into the atmosphere and then come down.

AMNA NAWAZ: In the minute or so we have left, I guess the question is, if they are detecting many more flying objects, at some point, there's a determination, some of them are enough of a threat to shoot down.

You have been inside NORAD there.

How is that decision made?

MAJ. GEN. SCOTT CLANCY: It's made through a complex web of categorization of those systems.

And the first step in that is identifying exactly what that is, and which is why NORAD launch aircraft to obtain visual identification of them prior to engaging them.

I think the predominant rationale or category or factor that was involved in these last three was the risk to civil aviation.

And that's why that decision was made at that time.

AMNA NAWAZ: That is retired Major General Scott Clancy, formerly director of operations at NORAD, joining us tonight.

Thank you for your time.

MAJ. GEN. SCOTT CLANCY: Thank you very much for having me.