The airspace above Reagan National Airport, where a commercial plane collided with an Army helicopter this week, has become increasingly congested with air traffic, including helicopters.
Among the unanswered questions about the crash near Washington, D.C., are the flight pattern of the Black Hawk helicopter and the exact nature of its training exercise.
Investigators say there are likely no survivors in the deadly aircraft collision that occurred Wednesday evening above the icy waters of the Potomac river.
