The Washington Post reported no survivors had been found as of late Wednesday local time (Thursday AEDT), and police have pulled multiple bodies from the water, citing officials.
A police official at the scene told CBS News there were three debris fields in the water. CBS reported at least 18 bodies had been recovered.
The American Airlines jet carrying 60 passengers and four crew collided with the helicopter while landing, prompting a large search-and-rescue operation in the nearby river.
Three soldiers were aboard the helicopter, which was on a training flight, a US official said.
Inflatable rescue boats were launched into the Potomac River from a point near the airport along the George Washington Parkway, just north of the airport.
Emergency personnel are continuing to work near the site of the crash. (AP PHOTO)
Officials did not provide a death toll from the collision. But US Senator Roger Marshall of Kansas, where the flight originated, suggested that all on board died, saying at a news conference at Reagan airport that "it's really hard when you lose probably over 60 Kansans simultaneously."
"When one person dies, it's a tragedy, but when many, many, many people die, it's an unbearable sorrow," he said. "It's a heartbreak beyond measure."
Jack Potter, the president and CEO of the Metropolitan Washington Airports Authority, emphasised at the same news conference that first responders were in "rescue mode."
Donad Trump questioned the actions of the helicopter crew and air traffic controllers. (AP PHOTO)
The Pentagon said it was launching an immediate investigation into the incident, which US President Donald Trump appeared to blame on the helicopter crew and air traffic controllers in a post on Truth Social.
"The helicopter was going straight at the airplane for an extended period of time. It is a CLEAR NIGHT, the lights on the plane were blazing, why didn't the helicopter go up or down, or turn," Trump wrote.
"Why didn't the control tower tell the helicopter what to do instead of asking if they saw the plane. This is a bad situation that looks like it should have been prevented. NOT GOOD!!!"
Air traffic control recordings appear to capture the final attempted communications with the helicopter, call sign PAT25, before it collides with the plane, described as CRJ.
"PAT25, do you have a CRJ in sight? PAT25, pass behind the CRJ," an air traffic controller says, according to a recording on liveatc.net.
Seconds later, another aircraft calls in to air traffic control, saying, "Tower, did you see that?" - apparently referring to the crash. An air traffic controller then redirects planes heading to runway 33 to go around.
Video of the crash captured by a webcam at the nearby Kennedy Centre showed the moment of impact between the aircraft and the helicopter, with a massive explosion lighting up the night sky.
Relatives gathered at the airport said they were getting little to no information from officials about the incident, adding that they were hearing more about the incident from news reports.
The plane carried a number of US ice skaters, family members and coaches returning from a camp following figure skating championships in Wichita, governing body US Figure Skating said.
Among those on board were Russian former figure skating world champions Yevgenia Shishkova and Vadim Naumov, Russian state media reported. The Kremlin offered condolences to the families of Russians killed, and said there were no plans for contacts for now between President Vladimir Putin and Trump.
Washington, DC, fire chief John Donnelly said at the news conference that at least 300 first responders were continuing to work on the "highly complex" rescue operation.
"Conditions out there are extremely rough for the responders," Donnelly said. "It's cold. They're dealing with windy conditions."
Asked by reporters whether there were any survivors, he responded that "we don't know yet."
Hypothermia is a concern for any possible survivors and first responders.
"At these frigid water temperatures, the human body's core temperature quickly drops. Exhaustion or unconsciousness can occur in as little as 15 to 30 minutes," AccuWeather Senior Director of Forecast Operations Dan DePodwin said.
Ronald Reagan Washington National Airport will remain closed until Friday AEDT. (AP PHOTO)
Airports authority CEO Potter said the airport would remain closed until at least 11am Thursday local time (Friday AEDT).
The last fatal crash involving a US commercial airline occurred in 2009 near Buffalo, New York. Everyone aboard the Bombardier DHC-8 propeller plane was killed including 45 passengers, two pilots and two flight attendants.
Agencies
