Pilots who land at Reagan National face a unique set of complications, including short runways, scores of helicopters and a mountain-size no-fly zone.
Radio traffic shows the air traffic controller did confirm with the helicopter that it had the airplane in sight two different times.
A 3D rendering shows the approximate altitude and paths of the plane and helicopter moments before the collision.
A passenger jet collided midair with a military helicopter near Reagan Airport, sending the aircraft into the icy Potomac River and leaving everyone on board feared dead.