President Joe Biden ordered the shootdown, which was announced from the White House.

On Feb. 4, another U.S. F-22 fighter jet brought down what the U.S. government called a Chinese surveillance balloon off the coast of South Carolina following its week-long journey across the United States and portions of Canada. China's government has said it was a civilian research vessel.

Some lawmakers criticized the president for not shooting down the Chinese balloon sooner. The U.S. military had recommended waiting until it was over the ocean out of fear of injuries from falling debris.

The Pentagon and the White House declined to give a detailed description of the latest object, saying only that it was far smaller than the Chinese balloon.

U.S. officials declined to speculate about what the object might be, even after a day of observation, raising questions about what kind of object could be so difficult to identify by experienced U.S. pilots and intelligence officials.

The Pentagon said it was first detected on Thursday using ground radars. F-35 aircraft were then sent to investigate. The UFO was flying at about 40,000 feet (12,190 meters) in a northeasterly direction, posing a risk to civilian air traffic.

The object was shot down off the coast of northeastern Alaska over frozen U.S. territorial waters near the Canadian border. Officials said it would be far easier to retrieve pieces of the object from the ice than it was with the Chinese balloon, pieces of which sank in the ocean when it was shot down.

UNMANNED VESSEL

Ryder said American pilots who flew alongside the latest object before it was downed determined that no human was aboard. He added it was incapable of manoeuvring and did not resemble an aeroplane. Ryder and other officials would not say whether it could simply be a weather balloon or another type of balloon.

"It wasn't an aircraft per se," Ryder told a news briefing.

The F-22 shot down the object at 1:45 p.m. EST.

Asked why Biden's authorization was necessary, Ryder acknowledged that the U.S. military commander overseeing North American airspace had the authority to shoot down objects that posed a military risk or risk to the American people.

"In this particular case, it was determined that this posed a reasonable threat to air traffic," Ryder said.

The Federal Aviation Administration (FAA) said it closed some airspace in northern Alaska to support Department of Defense activities.

Since the shootdown of the 200-foot-tall (60-meter-high) Chinese high-altitude surveillance balloon, U.S. officials have been scouring the ocean to recover debris and the undercarriage of electronic gadgetry.

Ryder told reporters "a significant" amount of the balloon had already been recovered or located, suggesting American officials may soon have more information about any Chinese espionage capabilities aboard the vessel.

After Friday's object was shot down, some lawmakers praised Biden.

"Glad to see the president act swiftly on this new intrusion to our airspace," Senator Mark Warner, chair of the Senate Intelligence Committee, said.

During an often contentious Senate hearing on Thursday, lawmakers criticized the Pentagon for not shooting down the Chinese balloon earlier, underscoring persistent concern in Congress about gaps in the U.S. ability to safeguard its airspace.