The Black Hawk military helicopter involved in Wednesday’s midair collision was training to evacuate government officials in the case of a catastrophic event when it crashed into an American Airlines regional passenger plane – creating a catastrophe of its own.

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.