The US Army helicopter that collided with a passenger jet in Washington was being operated on a training flight by a "fairly experienced crew" with night-vision goggles, as the Pentagon ordered a 48-hour pause in flying for the Virginia-based unit involved.
Authorities have said there were no survivors. Daniel Driscoll, US President Donald Trump's nominee for Army secretary, said the crash appeared to have been preventable.
The helicopter struck the jet near Ronald Reagan Washington National Airport, with both aircraft plunging into the Potomac River. The cause of the crash is under investigation. The airport is located in Arlington, Virginia, across the river from Washington.
"The people in the helicopter should have seen where they were going," Trump said at a White House press conference. He said at one point during the press conference that warnings by air traffic control were given too late.
"For some reason, you had a helicopter that was at the same height and going at an angle that was unbelievably bad."
In a video statement on Thursday, Defence Secretary Pete Hegseth said there was a crew of three soldiers on the training flight.
"It was a fairly experienced crew and it was doing a required annual night evaluation," he said.
"We anticipate that the investigation will quickly be able to determine whether the aircraft was in the corridor and at the right altitude at the time of the incident."
During an appearance later with Trump at the White House, Hegseth told reporters there appeared to have been an elevation issue with the Black Hawk, and said Army investigators were on the ground looking into the matter.
Jonathan Koziol, chief of staff of the Army's aviation directorate, told reporters that the instructor pilot, who was the designated pilot in command, had 1000 flying hours while the other pilot had 500 hours. The third soldier was a crew chief, typically riding in the back of the helicopter.
Koziol, a former Army aviator, said that the route over the Potomac, known as Route 4, was flown regularly by military pilots.
Koziol added that the crew members ordinarily would use visual cues and interact with air traffic control to ensure that they avoided any risk.
"This should not have been a problem," Koziol said, adding that the maximum altitude for Route 4 is 200 feet (60 metres). It is unclear how high the Black Hawk was flying.
At the White House, Trump and Hegseth said the era of diversity, equity and inclusion (DEI) was over in the government.
The Black Hawk crew included two male and one female soldier, an Army official said. There are female service members throughout the military, including as pilots.
"As for women in the military, flying a helicopter is like driving a car. You just got to learn how to do it and anyone can do it with the proper training," Koziol said.
The helicopter was from the 12th Aviation Battalion, which is based at Fort Belvoir in Virginia. The unit, which is responsible for helicopter flights in the US capital area and can be used to carry senior US government officials, will be grounded for 48 hours, Hegseth said. Reuters was first to report on the operational pause.
Driscoll appeared on Thursday at his confirmation hearing before the Senate Armed Services Committee.
"I am seeing the same things I believe you are, on television. It is an accident that seems to be preventable from what we can tell today," Driscoll told the senators.
Driscoll added that if he was confirmed there would be a focus on a culture of safety in the Army.
"I think we might need to look at where is an appropriate time to take training risk, and it may not be near an airport like Reagan," Driscoll added.
Military helicopters are a common sight around the Washington region that is home to numerous military bases. It is not uncommon for the military to order pauses after accidents or crashes.
