The service is often responsible for ferrying lawmakers and other V.I.P.’s across the area, and near Reagan National Airport.

The crash of an American Airlines passenger jet and a U.S. Army Black Hawk helicopter near Reagan Washington National Airport on Wednesday highlighted issues around the congested airspace shared by civilian and military aircraft over the U.

An American Airlines flight has collided in mid-air with a helicopter in Washington DC, with both crashing in the Potomac River.