An American Eagle jet and an Army helicopter collided over Washington on Wednesday night. The number of casualties is unclear, and a search-and-rescue mission is ongoing.

"Obviously, that will be fluid," John Potter, President and CEO of the Metropolitan Washington Airports Authority, said at a press conference early Thursday morning.Start the day smarter. Get all the news you need in your inbox each morning.

ARLINGTON, Va. (AP) — A passenger jet collided Wednesday with an Army helicopter while landing at Ronald Reagan National Airport near Washington, prompting a large search-and-rescue operation in the nearby Potomac River.