The Black Hawk helicopter that collided with a passenger jet in Washington on Wednesday was on a training flight along a route core to a seldom-discussed military mission to evacuate senior officials to safety in the event of an attack on the U.S., officials say.

There are confirmed fatalities from the collision of American Airlines Flight 5342 and the U.S. Army Black Hawk helicopter over the Potomac River. Several bodies have been pulled from the Potomac River crash site, according to two law enforcement sources familiar with the ongoing operation.