As an aside, 60 minutes talked with one of the DCA controlers whose shift ended right before our figure skating family sustained a tragic loss.
You can watch it on line. Half the controlers who are offered positions at DCA turn them down when they see how unsafe they are. That runway is the busiest in the country, yet congress keeps adding flights to it. 60 min does a simulation of what the chopper pilot would have seen. There is no way they could have seen the jet untill the last few seconds....light polution. This is a govt owned airport and the head of the Ntsb and controllers union ripped congress a new one....yet Congress and the head of the FAA and the Transportation secretary still do practically nothing.
If you watch the interview, bring a box of kleenex. IIRC, a past Blackhawk pilot's son was the co pilot.