The Chinese authorities say a surveillance balloon sighted over sensitive US territory is theirs, but insist its purpose is for weather research and that it was blown off course by unexpected winds.
We've looked at the prevailing wind patterns and data modelling to track its possible path.
Where has the balloon been seen?
It was monitored travelling across Canadian territory before appearing over the city of Billings in Montana on Wednesday, where it was spotted in the sky by city residents.
US authorities say they've been tracking the balloon across US airspace using manned aircraft, and that it's been flying over sensitive military areas.