Air traffic controllers asked Flight 5342 to switch runways when coming in to land. Black box recordings from the jet and the military helicopter it collided with will help reveal whether this contributed to the accident.

The flight data recorder and cockpit voice recorder, known as the black boxes, may offer clues about what went wrong before the crash.

One air traffic controller was doing work normally assigned to two people in the tower at Reagan National when the collision happened, according to a report by the Federal Aviation Administration obtained by The Associated Press.

NBC News' Tom Costello reports on how the air traffic control staffing at Reagan Washington National Airport (DCA) was "allowed, but not ideal," under the FAA’s safety standards.