Washington: Three unusual aircraft have been shot down by US fighter jets over North America this month, incidents that have alarmed US and Canadian lawmakers and ignited debate over the safety of the continent's skies.
All three objects, which officials say violated Canadian and American airspace, were downed by F-22s, and debris is being analyzed by experts to glean more details.
Here's a timeline of what happened and everything we know about the objects so far.
Feb. 4: Chinese surveillance balloon, shot down off South Carolina
On Jan. 28, a mysterious floating object entered American airspace, although US officials did not acknowledge the balloon publicly until Feb. 2.
On Jan. 30, the balloon entered Canadian airspace before floating back over the United States on Jan. 31, in northern Idaho.
On Feb. 1, President Biden authorised the military to take down the balloon, instructing the Pentagon to act "as soon as the mission could be accomplished without undue risk to American lives." With a single missile, an F-22 Raptor shot down the balloon off South Carolina's coast on Feb. 4.
The US intelligence community identified the object as a Chinese spy balloon and linked it to a surveillance program run by China's People's Liberation Army. The Pentagon said the object was being used to gather intelligence on US military installations.
Chinese officials said the object was a data-gathering weather balloon that strayed into US airspace, and China's Foreign Ministry said in a statement on Feb. 5 that the downing was "a clear overreaction" and "a serious violation of international practice."
US officials said earlier this month that a second suspected spy balloon was spotted over Latin America and that a third is probably operating elsewhere.
Feb. 10: 'High-altitude object' downed over Alaska
A pair of F-22 Raptors took down an object roughly the size of a small car over the coast of northeastern Alaska on Friday. Biden was notified about the second object the day before and ordered the hit, National Security Council spokesman John Kirby said.
Fighter aircraft were dispatched to observe the object more closely, soon determining that there was no pilot onboard, he said.
The Pentagon said the object posed a threat to civilian air traffic because it operated at an altitude of 40,000 feet, unlike the balloon, which flew at 60,000 to 65,000 feet. It was shot down and landed in freezing, territorial waters.
Kirby said that the military action was taken out of an "abundance of caution" and that officials do not know where the object came from or why it was floating in US airspace.
"We don't know what entity owns this object," Kirby said Friday. "There's no indication it's from a nation or an institution or an individual."
The recovery operation, complicated by winter weather is underway.
Feb. 11: 'Cylindrical' object shot down over Canada
An F-22 Raptor shot down a "high-altitude airborne object" over Canada's Yukon territory on Saturday, the third craft to be intercepted by the military in eight days.
NORAD, the organisation made up of US and Canadian military personnel to safeguard North America's skies, first detected the object on Friday evening, and it was monitored by officials on Friday night and Saturday.
Canadian Defense Minister Anita Anand said the mysterious object was "cylindrical in nature."
An AIM-9X Sidewinder missile was used to down the object following a discussion between Defense Secretary Lloyd Austin and Anand, said Air Force Brig. Gen. Patrick Ryder, a Pentagon spokesman.
Canadian Prime Minister Justin Trudeau said on Saturday on Twitter that he had spoken to Biden and ordered the takedown of the object, which "violated Canadian airspace." Flights were temporarily restricted in northern Montana on Saturday night.
"Canadian and US aircraft were scrambled, and a US F-22 successfully fired at the object," Trudeau said. Ryder said that Canadian forces would work alongside the FBI to examine the remains of the object.
Biden was "continually briefed by his national security team," a statement from the White House said Saturday amid news of the third mysterious object.