A major search and rescue operation is underway in Washington DC after an American Airlines plane collided midair with an army helicopter and crashed into a river.

There are unconfirmed numbers of fatalities and all takeoffs and landings from Ronald Reagan National Airport were halted on Wednesday night (local time).

The jet was reportedly carrying 60 passengers and there were four crew on the Black Hawk army helicopter.

The collision happened about 9pm as the plane, which had travelled from Kansas, was coming in for landing.

The large search-and-rescue operation was underway Thursday afternoon (AEDT) in the Potomac River, with agency helicopters flying over the scene looking for survivors.

Inflatable rescue boats were launched into the river from a point near the airport along the George Washington Parkway.

American Airlines told CNN there were 60 passengers and four crew on Flight 5342, which had departed from Wichita in Kansas.

US defence sources said there were three soldiers aboard the Blackhawk.

President Donald Trump said he had been “fully briefed on this terrible accident” and, referring to the passengers, added, “May God Bless their souls.”

US Senator Ted Cruz tweeted that there had been an unconfirmed number of fatalities.

Vice President JD Vance encouraged followers on the social media platform X to “say a prayer for everyone involved”.

The Federal Aviation Administration said the midair collision occurred when the regional jet crashed into a military Blackhawk helicopter while on approach to an airport runway.

In audio from the air traffic control tower around the time of the crash, a controller is heard asking the helicopter, “PAT25 do you have the CRJ in sight”, in reference to the passenger aircraft.

“Tower did you see that?” another pilot is heard calling seconds after the apparent collision.

The tower immediately began diverting other aircraft from Reagan.

The collision occurred in some of the most tightly controlled and monitored airspace in the world, just over three miles south of the White House and the Capitol.

Investigators will try to piece together the aircrafts’ final moments before their collision, including loss of altitude by the passenger jet.

American Airlines flight 5342 was inbound to Reagan National at an altitude of about 120 metres and a speed of about 220kmh when it suffered a rapid loss of altitude over the Potomac River, according to data from its radio transponder.

The Canadian-made Bombardier CRJ-701 twin-engine jet was manufactured in 2004 and can be configured to carry up to 70 passengers.

A few minutes before landing, air traffic controllers asked the arriving commercial jet if it could land on the shorter Runway 33 at Reagan National and the pilots said they were able.

Controllers then cleared the plane to land on Runway 33. Flight tracking sites showed the plane adjust its approach to the new runway.

Less than 30 seconds before the crash, an air traffic controller asks the helicopter if it has the arriving plane in sight.

The controller makes another radio call to the helicopter moments later: “PAT 25 pass behind the CRJ.” Seconds after that the two aircraft collide.

The plane’s radio transponder stopped transmitting about 2400 feet short of the runway, roughly over the middle of the river.

The tower immediately began diverting other aircraft from Reagan.

Video from an observation camera at the nearby Kennedy Center showed two sets of lights consistent with aircraft appearing to join in a fireball.

The crash is serving as a major test for two of the Trump administration’s newest agency leaders. Pete Hegseth, sworn in days ago as defence secretary, posted on social media that his department was “actively monitoring” the situation that involved an Army helicopter.

Transportation Secretary Sean Duffy, just sworn in earlier this week, said in a social media post that he was “at the FAA HQ and closely monitoring the situation”.

The incident recalled the crash of an Air Florida flight that plummeted into the Potomac on January 13, 1982, that killed 78 people. That crash was attributed to bad weather.

The last fatal crash involving a US commercial airline occured 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.

Another person on the ground also died, bringing the total death toll to 50. An investigation determined that the captain accidentally caused the plane to stall as it approached the airport in Buffalo.

-with AAP