The airspace over Lake Michigan in the northern United States has been closed for " national defense
" reasons
, the US civil aviation regulator (FAA) announced on Sunday.
The news comes as three flying objects, including one described by Washington as a Chinese spy balloon, were shot down in a week over the United States and Canada.
On Saturday, airspace in the US state of Montana was temporarily closed, but a fighter jet dispatched to investigate a "
radar anomaly
" did not identify a
flying "
object ", according to the military.