The way an object moves in the sky can also reveal whether it's a drone or a plane, he said. Drones tend to hover, make abrupt directional changes, or move erratically, owing to their small size and agility. Manned aircraft follow smooth, linear flight paths, especially in controlled airspace, where their routes are more predictable.

Members of the US House Intelligence Committee, who were given a closed-door briefing on Tuesday, joined Biden on Wednesday in trying to reassure the public. Among the committee members who spoke to reporters afterwards were Chrissy Houlahan,