The collision occurred late evening on Wednesday as the airliner came into land after a routine flight from Wichita, Kansas.
Reagan National is a major airport located a short distance from downtown Washington, the White House and the Pentagon.
The airspace is extremely busy, with civilian and military aircraft almost constantly moving in the area.
“I think there are a lot of speculations at this stage, and the investigation hasn’t really begun,” Hassan Shahidi, chief executive of the independent Flight Safety Foundation, told AFP.
“There are different shifts … that come in and are put together with the right staff to handle the amount of traffic.
“Sometimes air traffic controllers handle one frequency. Sometimes they handle two frequencies. Sometimes they handle more than two frequencies.
“That is all dependent on the situation, on the traffic level, and the time of day. This was at night, at 9pm, when the traffic is subsiding.”
