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.

Dozens of people are dead after a regional jet collided with an Army Black Hawk helicopter Wednesday night over Washington, D.C., officials said, the nation's first major commercial airline crash since 2009.