A Timeline of the U.F.O.s That Were Shot Down This Weekend

The U.S. military shot down at least three unidentified flying objects over the weekend after a Chinese spy balloon that had invaded American airspace was downed on Feb. 4, setting off a diplomatic crisis.

At this point, it is unclear what the objects were, their purpose or who sent them.

What is clear is that the United States and Canada have become hypervigilant since the balloon incursion. The North American Aerospace Defense Command, or NORAD, has adjusted its radar system to become more sensitive, sharply raising the number of objects it detects.

Here’s a quick timeline of events.

Feb. 4: A Chinese spy balloon is shot down over the Atlantic Ocean.

The balloon entered Alaskan airspace on Jan. 28, Pentagon officials said, and later drifted from Idaho southeast to the Carolinas before it was shot down on Feb. 4, off the coast of South Carolina.

A F-22 fighter jet fired a Sidewinder air-to-air missile at the balloon, which was about the size of three buses and was flying at an altitude of 60,000 to 65,000 feet.

Secretary of State Antony J. Blinken subsequently canceled a trip to China that would have been the first by a Biden cabinet secretary.

American officials have said they believe the balloon was meant to conduct surveillance on U.S. military bases, although China has maintained that the device was a civilian aircraft that strayed into American airspace. On Monday, a Chinese official said unauthorized balloons from the United States had flown over Chinese airspace more than 10 times since the start of last year.

Feb. 10: A U.F.O. is shot down off Alaska.

On Friday, a U.S. fighter jet brought down an unidentified object over the waters of Alaska. The object broke into pieces after being shot down and was most likely not a balloon, a Defense Department official said. A White House official said the object was the size of a small car.

The object was first detected on Thursday night, Alaskan time, and was headed toward the North Pole before it was struck down.

Feb. 11: A U.F.O. is shot down over Canada.

An American F-22 fighter downed another object on Saturday over the Yukon Territory, which borders Alaska. The object, which a Canadian official described as cylindrical and smaller than the spy balloon, was picked up on radar late Friday as it passed over Alaska.

Feb. 12: A U.F.O. is shot down over Lake Huron.

An object that first appeared over Montana on Saturday reappeared on Sunday before being shot down over Lake Huron off Michigan. The object, which was flying at 20,000 feet, had an octagonal structure with strings hanging off but had no discernible payload, U.S. officials said.

National security officials on Sunday discounted the possibility that the objects shot down over the weekend might have extraterrestrial origins. However, Gen. Glen D. VanHerck, the commander of the Air Force’s Northern Command, said during a news conference, “I haven’t ruled out anything at this point.”