A US fighter jet shot down an unidentified object over Canada on Saturday -- in a joint operation by the North American neighbors and the second such take-down in their skies since the dramatic downing of a suspected Chinese spy balloon a week ago. Prime Minister Justin Trudeau said he ordered the takedown of the object, the latest of a series of mysterious air intrusions. "Canadian and US aircraft were scrambled, and a US F-22 successfully fired at the object," Trudeau tweeted Saturday.