The US on Sunday shot down a high-altitude service balloon belonging to China that was suspected to be spying over strategic sites in the US, as per a statement from Secretary of Defence Lloyd J Austin. A US military aircraft successfully brought down shot the suspected spy balloon off the coast of South Carolina, in an area that didn't risk harming citizens with debris.
While China has angrily voiced its "strong dissatisfaction" at the move and said it may make "necessary responses", here's what we know about spy balloons.
Cheap, quiet, and hard to reach -- these balloons have long been used for reconnaissance purposes, including in conflicts like the American Civil War. The practice became widespread during World War I and was used extensively during the Cold War, when the US launched hundreds of balloons to gather intelligence on the Soviet Union and China.
While their use has declined with the rise of unmanned drones and satellites, many countries still employ spy balloons. The Pentagon is expanding investment in high-altitude inflatables, Politico reported last year. Modern balloons are generally unmanned, but they still generally lack propulsion and are subject to wind currents.
Watch: The moment US fighter jet shot down Chinese 'spy' balloon
A balloon the size of three school buses
The Chinese spy balloon which was shot down on Sunday was about the size of three school buses, US officials said. It moved east over America at an altitude of about 60,000 feet. The US says it was being used for surveillance and intelligence collection.
US defense and military officials said Saturday that the balloon entered the US air defense zone north of the Aleutian Islands on January 28 and moved over land across Alaska and into Canadian airspace in the Northwest Territories on January 30. The next day it crossed back into US territory over northern Idaho.
(With inputs from Bloomberg and agencies)