Washington DC - All 64 people on board the American Airlines passenger jet and all three soldiers on board the US army helicopter that collided over Washington are presumed dead, officials said on Thursday after an overnight search operation in the icy Potomac River.

"At this point, we don't believe there are any survivors from this accident," Washington fire chief John Donnelly said at a morning press conference.

Donnelly said that the bodies of 27 people on the plane – which had several top figure skaters on board – and one from the helicopter have been recovered from the river.

"We are now at a point where we are switching from a rescue operation to a recovery operation," he said.

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American Airlines Flight 5342 was travelling from Wichita, Kansas to Washington's Reagan National Airport when it collided with the Black Hawk military helicopter as it was approaching the runway shortly before 9 PM ET on Wednesday, sending both aircraft plummeting into the river.

Some 300 emergency responders deployed to locate survivors were racing against time as they searched the dark and icy waters.

The Pentagon said the Black Hawk army helicopter had been on a training flight when colliding with the plane.

American Airlines chief Robert Isom said the cause of the accident was still unclear.

President Donald Trump suggested that failures on part of the helicopter's pilot might have caused the midair collision.

"You had a pilot problem, from the standpoint of the helicopter," Trump said during a news briefing at the White House on Thursday, claiming with no evidence that the army helicopter could have changed its course to avoid colliding with the American Airlines plane.

He also criticized air traffic control at Reagan Washington National Airport for taking too long to send out a warning, and baselessly blamed diversity, equity, and inclusion (DEI) policies at the Federal Aviation Administration (FAA) for the crash.

Turning the tragedy into political fodder, he falsely said FAA included "focus on hiring people with severe intellectual and psychiatric disabilities."

The National Transportation Safety Board (NTSB), which is leading the investigation into the collision, asked for time to evaluate all the data before allocating fault.

"You need to give us time," NTSB chair Jennifer Homendy said in a press briefing. "It's not that we don't have information, we do have information. We have data we have substantial amounts of information we need to verify ... we need to take our time to make sure it is accurate."

"As part of any investigation, we look at the human, the machine and the environment," Homendy said. "So we will look at all the humans that were involved in this accident."

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Around 50 investigators are at work at the scene of the accident. In addition, there are specialists at the agency's headquarters who are familiar with the case.

Another agency representative, Todd Inman, also stressed: "Our intention is to have a preliminary report within 30 days and the final report will be issued once we've completed all of our fact finding and investigation.

"Now, we will not be determining the probable cause of the accident while we are here on the scene, nor will we speculate about what may have caused this accident."

One of the plane's black boxes was recovered later on Thursday.