WASHINGTON — A U.S. military fighter jet shot down an unknown object flying off the remote northern coast of Alaska on Friday on orders from President Joe Biden, White House officials said.

White House National Security Council spokesman John Kirby said the object was downed because it was flying at about 40,000 feet and posed a “reasonable threat” to the safety of civilian flights, not because of any knowledge that it was engaged in surveillance. Asked about the object’s downing, Biden on Friday said only that “It was a success.”

Commercial airliners and private jets can fly as high as 45,000 feet.

Kirby described the object as roughly the size of a small car, much smaller than the massive suspected Chinese spy balloon downed by Air Force fighter jets Saturday off the coast of South Carolina after it transited over sensitive military sites across the continental U.S.

The twin downings in such close succession are extraordinary, and reflect heightened concerns over China’s surveillance program and public pressure on Biden to take a tough stand against it. Still, there were few answers about the unknown object downed Friday and the White House drew distinctions between the two episodes. Officials couldn’t say if the latest object contained any surveillance equipment, where it came from or what purpose it had.

The Pentagon on Friday declined to provide a more precise description of the object, only saying that U.S. pilots who flew up to observe it determined it didn’t appear to be manned. Officials said the object was far smaller than the previous balloon, did not appear to be maneuverable and was traveling at a much lower altitude.

Kirby maintained that Biden, based on the advice of the Pentagon, believed it posed enough of a concern to shoot it out of the sky — primarily because of the potential risk to civilian aircraft.

“We’re going to remain vigilant about our airspace,” Kirby said. “The president takes his obligations to protect our national security interests as paramount.”

The president was briefed on the presence of the object Thursday evening after two fighter jets surveilled it.

Brig. Gen. Pat Ryder, Pentagon press secretary, told reporters Friday that an F-22 fighter aircraft based at Alaska’s Joint Base Elmendorf-Richardson shot down the object using an AIM-9X short-range air-to-air missile, the same type used to take down the balloon nearly a week ago.

The object flew over one of the most desolate places on the nation. Few towns dot Alaska’s North Slope, with the two apparently closest communities — Deadhorse and Kaktovik — combining for about 300 people. Unlike the suspected spy balloon, which was downed to live feeds and got U.S. residents looking up to the skies, it’s likely few people saw this object given the blistering frigid conditions of northern Alaska this time of the year, meaning there are few people outside for a prolonged period of time.

Ahead of the the shoot-down, the Federal Aviation Administration restricted flights over a roughly 10-square mile rea within U.S. airspace off Alaska’s Bullen Point, the site of a disused U.S. Air Force radar station on the Beaufort Sea about 100 miles from the Canadian border, inside the Arctic Circle.

Canadian Prime Minister Justin Trudeau said in a tweet Friday that he had been briefed and supported the decision. “Our military and intelligence services will always work together,” he said.

The object fell onto frozen waters and officials expected they could recover debris faster than from last week’s massive balloon. Ryder said the object was traveling northeast when it was shot down. He said several U.S. military helicopters have gone out to begin the recovery effort.

The unknown object was shot down in an area with harsh weather conditions and about six and a half hours of daylight at this time of year. Daytime temperatures Friday were about minus 17 degrees Fahrenheit.

After the object was detected Thursday, NORAD — North American Aerospace Defense Command —sent F-35s to observe it, a U.S. official said, adding that the military queried U.S. government agencies to make sure it did not belong to any of them, and had confidence it was not a U.S. government or military asset. The official was not authorized to speak publicly about sensitive national security matters and spoke on condition of anonymity.

Because it was much smaller than the suspected Chinese spy balloon, there were fewer safety concerns about downing it over land, so the decision was made to shoot it down when it was possible. That happened over water.

The development came almost a week after the U.S. shot down a suspected Chinese spy balloon off the Carolina coast after it traversed sensitive military sites across North America. China insisted the flyover was an accident involving a civilian craft and threatened repercussions.

Biden issued the order but had wanted the balloon downed even earlier. He was advised that the best time for the operation would be when it was over water. Military officials determined that bringing it down over land from an altitude of 60,000 feet would pose an undue risk to people on the ground.

The balloon was part of a large surveillance program that China has been conducting for “several years,” the Pentagon has said. The U.S. has said Chinese balloons have flown over dozens of countries across five continents in recent years, and it learned more about the balloon program after closely monitoring the one shot down near South Carolina.

China responded that it reserved the right to “take further actions” and criticized the U.S. for “an obvious overreaction and a serious violation of international practice.”