The plane was on its way in for landing at Ronald Reagan Airport on Wednesday evening when its path was crossed by the helicopter.
The boxes, in the form of the sound recorder that records sounds from the cockpit and the flight recorder that, among other things, registers the plane's altitude, speed, and direction – are now to be analyzed.
The American aviation authority FAA wrote in a preliminary report on Thursday that the staffing in the control tower was not at a normal level considering the time and air traffic at the time, according to The New York Times.
The plane crash is the worst in the USA since November 2001 when an American Airlines plane crashed shortly after taking off from JFK Airport in New York. Then, all 260 on board and five people on the ground were killed.
