Media companies reported earlier in the night local time that tens of bodies have been found in the cold Potomac River.
Early in the morning, Fire Chief John Donnelly then declared the hope lost.
This is now transitioning from a rescue to a recovery operation, he said.
The plane was on its way in for landing at Ronald Reagan Airport on Wednesday evening when its path was crossed by the helicopter. Images from surveillance cameras show how they exploded together over the Potomac.
"Not normal" staffing
The Washington plane was from a subsidiary of major American Airlines and came from Wichita in Kansas. The helicopter is said to have been on a training exercise from the Davison Army Airfield, a few miles south. But many on social media are wondering how it could have been in the vicinity of the approach to one of the USA's larger civilian airports.
Trump's controversial Defense Minister Pete Hegseth writes on X that the army and the Defense Department have immediately launched their own investigation.
The American aviation authority FAA writes in a preliminary report on the incident that the staffing in the air traffic control tower was not at a normal level considering the time and air traffic at the time, writes The New York Times.
The air traffic controller who was responsible for the helicopters in the airport's vicinity also had responsibility for directing planes taking off and landing. Usually, two air traffic controllers share these tasks.
Worst in over 20 years
In radio communication with the air traffic control tower, it emerges that they realized what was about to happen just a few seconds before the accident, reports American media.
PAT25 (the helicopter), do you see CRJ (the plane)? asks the tower, and then instructs:
PAT25, go behind CRJ.
There is silence for a number of seconds, then voices are heard exclaiming "oh!" and "oh, God!".
Tower, did you see that? asks a pilot on another plane.
The plane crash is the worst in the USA since November 2001 when an American Airlines plane crashed shortly after takeoff from JFK Airport in New York. Then, all 260 on board and five people on the ground were killed, writes CNBC.
