In recent weeks, three unidentified objects in North American airspace have been shot down.
Last Saturday, the United States destroyed a suspected Chinese spy balloon, and this weekend two more objects were shot down over Alaska and the Yukon, one of which flew over Canada.
It remains unclear if the objects shot down over the weekend were spy balloons.
But in an interview with ABC News, Democratic Majority Leader Chuck Schumer, who spoke with White House National Security Adviser Jake Sullivan, said it was likely two more balloons.
However, they should have been smaller than the Chinese balloon that was shot down on February 4.
- We didn't know about these balloons until a couple of months ago.
Our intelligence service and military did not know about them, he tells ABC News.
A new ignition
Spy balloons are not a new phenomenon, but were already used in the American Civil War, says Mattias Abrahamsson, formerly responsible for balloon projects at the Esrange space base.
But after being overshadowed by drones and satellites, the spy balloon may once again be in the air.
"Essentially, balloons are cheap, easy to launch and have the desired effect," says John Blaxland, professor of international security and intelligence studies at the Australian National University, adding:
- With the help of microtechnology and AI, you can quickly collect and send information to your home country in real time, he adds.
Watch experts John Blaxland and Mattias Abrahamsson explain the strengths and weaknesses of spy balloons in the video above.