The crew of the Army helicopter that collided with an American Airlines jet may have had inaccurate altitude readings in the moments before the crash, investigators have said.

The soldiers may also not have heard key instructions from air traffic controllers to move behind the plane, it was revealed.

NTSB chair Jennifer Homendy said the recording from the Black Hawk suggested an incomplete radio transmission may have left them without understanding how it should shift position just before the January 29 crash, in which all 67 aboard the two aircraft were killed.

'That transmission was interrupted - it was stepped on,' she said, leaving them unable to hear the words 'pass behind the' because the helicopter's microphone key was pressed at the same moment.

'At 8:47:42 - or 17 seconds before impact - a radio transmission from the tower was audible on both CVRs directing the Black Hawk to pass behind the CRJ,' Homendy told reporters.

'CVR data from the Black Hawk indicated that the portion of the transmission that stated 'pass behind the' may not have been received by the Black Hawk crew.'

Homendy said the helicopter was on a 'check' flight that night where the pilot was undergoing an annual test and a test on using night vision goggles. 

Investigators believe the crew was wearing night vision goggles throughout the flight and that there was nothing to suggest that the crew had removed them.

She said that testing was underway to establish what both crews were able to see at the time of the collision. 

Shortly before the collision, a controller got an alert that the plane and Black Hawk were converging and asked the helicopter if it had the plane in sight. 

The military pilot said yes and asked for 'visual separation' with the jet - allowing it to fly closer than otherwise may have been allowed if the pilots didn't see the plane. Controllers approved the request.

Roughly 20 seconds later, the aircraft collided.

Since the crash, the National Transportation Safety Board has recovered all the flight data recorders and pulled the wreckage of both aircraft from the Potomac. 

Last week it was revealed how vital tracking technology inside the helicopter was turned off for 'no compelling reason' when it collided.

The Black Hawk was performing a routine training mission in an effort to renew 28-year-old Captain Rebecca M. Lobach's annual certification.

When the chopper went down, the Black Hawk's Automatic Dependent Surveillance-Broadcast was disabled - a system which shares an aircraft's position, altitude and speed, Sen. Ted Cruz told the New York Times.

The technology also includes a display that shows pilots the location of other aircrafts both in the sky or on a runway, and allows air traffic controllers to not just rely on radar tracking - which could have a delay of a few seconds.

Military helicopters can turn off the ADS-B during 'continuity of government' missions so that nobody can track where government officials are being flown.

It will take more than a year to get the final NTSB report on the collision, and Homendy warned reporters that many issues were still being probed.

'We're only a couple weeks out,' from the crash, she said. 'We have a lot of work to do.' 

Last week the Federal Aviation Administration revealed how it is set to reduce the number of arrivals at Washington Reagan National Airport in DC, following the deadly accident. 

The FAA said there would be reduction from a maximum of 28 to 26 arrivals per hour would reduce future risks - but would also increase average delays from 40 minutes to 50 minutes. 

An email explained how investigators from the FAA and National Transportation Safety Board 'have expressed concern for our tower personnel on duty, who have an increased level of stress while also having a front row view of the accident recovery.'

The email added that reducing the rate from 28 to 26 'will reduce risk and allow a little space for extra coordination.'

Chris Rocheleau was appointed as acting head of the FAA by Donald Trump the morning after the disaster - and on January 30, the President signed a memorandum in the Oval Office, ordering an immediate assessment of aviation safety.

Reagan National Airport is notoriously crowded, and the crossover in the air space between jets and helicopters is routine - but has caused pilots issues for decades. 

But since the catastrophe, aviation experts have sounded the alarm over the dangerous airspace over Reagan International Airport as they described last week's American Airlines crash as a 'disaster waiting to happen.' 

Data from the FAA found there were over 30 reports of 'near-midair collisions' over the airport as far back as 1987, with at least 10 involving military aircraft, according to NPR. 

The collision was he deadliest plane crash in the U.S. since 2001, when a jet slammed into a New York City neighborhood just after takeoff, killing all 260 people on board and five more on the ground.

The collision likely occurred at an altitude of about 325 feet, investigators have said, which would put the Black Hawk above its 200-foot limit for that location.

Cockpit conversations a few minutes before the crash indicated conflicting altitude data, Homendy said, with the helicopter's pilot calling out that they were then at 300 feet, but the instructor pilot saying it was 400 feet. 

'We are looking at the possibility there may be bad data,' she said.

That generation of Black Hawks typically has two types of altimeters - one relying on barometric pressure and the other on radio frequency signals bounced off the ground. 

Helicopter pilots typically rely on barometric readings while flying, but the helicopter's black box captures its radio altitude.

The radio altitude at the time of the impact put the Black Hawk at 278 feet, Homendy said.

'But I want to caution, that does not mean that's what the Black Hawk crew was seeing on the barometric altimeters in the cockpit,' she said. 'We are seeing conflicting information in the data.'

The Army has said the Black Hawk crew was highly experienced, and accustomed to the crowded skies around the nation's capital.

Investigators also said that about a second before impact, the jet's flight recorder showed a change in its angle, though they did not say whether that indicated the pilots were trying to perform an evasive maneuver to avoid the crash. 

Aside from Captain Lobach of Durham, North Carolina; the other two crew members on the chopper were Staff Sgt. Ryan Austin O'Hara, 28, of Lilburn, Georgia; and Chief Warrant Officer 2 Andrew Loyd Eaves, 39, of Great Mills, Maryland. O'Hara was the crew chief and Eaves and Lobach were pilots.

Lobach's friends and fellow soldiers called her deeply meticulous, 'brilliant and fearless.'

The American Airlines jet, which was flying from Wichita, Kansas, and preparing to land at the time of the crash, was piloted by 34-year-old Jonathan Campos, whose relatives said had dreamed of flying since he was 3.

The passenger plane recorded its altitude at 313 feet two seconds before collision.

A few minutes before the twin-engine jet was to land, air traffic controllers asked if it could use a shorter runway. The pilots agreed, and flight-tracking sites show the plane adjusted its approach. 

The jet's passengers ranged from a group of hunters to students and parents from northern Virginia schools to members of the Skating Club of Boston. 

They were returning from a development camp for elite junior skaters that followed the 2025 U.S. Figure Skating Championships in Wichita.

Almost immediately after the crash, President Donald Trump publicly faulted the helicopter for flying too high. 

He also blamed federal diversity and inclusion efforts, particularly regarding air traffic controllers. 

When pressed by reporters, the president could not back up those claims. A few days later, Trump placed the blame on what he called an 'obsolete' air traffic control system.