Unclear how 'objects' are staying aloft, senior U.S. general says

The U.S. military commander who safeguards U.S. airspace said on Sunday he could not determine how the latest three objects shot down over the past three days were staying aloft, adding he was not calling them balloons for a reason.

"I'm not able to categorize how they stay aloft. It could be a gaseous type of balloon inside a structure or it could be some type of a propulsion system," Air Force General Glen VanHerck, head of U.S. North American Aerospace Defense Command (NORAD) and Northern Command told reporters.