According to this report, one air traffic controller was doing the job of two controllers at the time of the crash.
>>>Staffing at the air traffic control tower at Ronald Reagan National Airport was “not normal for the time of day and volume of traffic,” according to an internal preliminary Federal Aviation Administration safety report about the collision that was reviewed by The New York Times.
The controller who was handling helicopters in the airport’s vicinity Wednesday night was also instructing planes that were landing and departing from its runways.
Those jobs typically are assigned to two controllers, rather than one.<<<
It's temping to blame it on this, but of course we don't know the cause right now.
Regardless of the cause, it is tragic.