Watch: First responders at scene of plane crash in Washington DC
A passenger plane carrying 64 passengers and crew has crashed into a river in Washington DC after it collided in mid-air with a US Army helicopter.
Eighteen bodies have been pulled from the Potomac River so far, where search and rescue teams are scouring the waters in freezing temperatures, according to a police official who spoke to the BBC's broadcast partner, CBS News.
Authorities are investigating, and the nearby Ronald Reagan Washington National Airport has grounded all flights.
What happened?
At around 21:00 local time (02:00 GMT) on Wednesday, a PSA Airlines jet operating as American Airlines 5342 collided with a US Army helicopter as it approached Ronald Reagan Washington National Airport, according to the Federal Aviation Administration (FAA).
The passenger plane, a Bombardier CRJ700, departed from Wichita, Kansas and was carrying 60 passengers and four crew, American Airlines said.
The Pentagon said the helicopter involved was a Sikorsky H-60 that took off from Fort Belvoir in Virginia.
Three US soldiers were on board, Washington DC Mayor Muriel Bowser said. Another official said it was on a training flight, and it belonged to B Company, 12th Aviation Battalion from Fort Belvoir in Virginia.
A clip published online, and reviewed by CNN, purports to capture the air traffic control conversation in the moments before the crash. A controller can reportedly be heard warning the helicopter about the plane, but receiving no reply. The audio has not been verified by the BBC.
The FAA said it would investigate the incident, together with the National Transportation Safety Board (NTSB).
Were there casualties?
Officials in Washington DC have refused to confirm reports on casualties during a press conference, saying they are focused on continuing their rescue effort through the night - which they describe as challenging.
However, a police official at the scene told CBS that 18 bodies had been pulled from the water.
US Figure Skating said "several members of our skating community were sadly aboard" the flight. It said this group comprised athletes, coaches and family members who were returning home from a development camp in Kansas.
Early reports in US media said the passenger plane could be seen split in half on the Potomac River, while the helicopter was upside down in the water.
About 300 responders on rubber boats have been deployed to search for survivors, said Washington DC Fire and Emergency Services Chief John Donnelly.
"The challenge is access, there is wind, pieces of ice (on the water). It is dangerous and hard to work in," he said.
What are eyewitnesses saying?
Ari Schulman told NBC Washington that he saw the plane crash while driving on the George Washington Parkway, which runs along the airport.
He said the plane's approach looked normal, until he saw the aircraft bank hard to the right, with "streams of sparks" running underneath, illuminating its belly.
At that point, he said he knew that it looked "very, very wrong". Having seen plane landings there in the past, he said a plane's underside should not have been visible in the dark.
The sparks, he said, resembled a "giant roman candle" and went from the plane's nose to its tail.
Jimmy Mazeo said he saw the crash while having dinner with his girlfriend at a park near the airport.
He recalled seeing what looked like a "white flare" in the sky. He said planes flying into Ronald Reagan Airport appeared to have been flying in "irregular patterns".
Mr Mazeo said he did not think much of what he saw until emergency services started arriving at the scene.
Watch: Witness describes seeing ‘white flare’ at moment of plane collision
What are US officials saying?
President Donald Trump said he had been fully briefed on the the "terrible accident" and that he was monitoring the situation closely.
"May God Bless their souls," he said in a statement. "Thank you for the incredible work being done by our first responders.
On his TruthSocial social media account, he has also raised questions about how the incident could have happened, writing: "This is a bad situation that looks like it should have been prevented. NOT GOOD!!!"
Vice-President JD Vance asked for prayers for those who were in the incident.
Defence Secretary Pete Hegseth and Transportation Secretary Sean Duffy, whose appointments were just recently confirmed, also said they were monitoring the situation.
Asked if flight paths near Ronald Reagan airport would be changed after the incident, Duffy said "we will take appropriate action if necessary". He added: "There will be a review of what happened here tonight."
American Airlines CEO Robert Isom expressed his "deep sorrow" about the collision in a video which has been posted to the airline's website.
That was echoed by Roger Marshall, a US senator representing Kansas, where the plane had travelled from. He described a "heartbreak beyond measure".