WASHINGTON (AP) — The crew of the Army helicopter that collided in midair with an American Airlines jet near Washington, D.C.’s Ronald Reagan National Airport may have had inaccurate altitude readings in the moments before the crash, and also may not have heard key instructions from air traffic controllers to move behind the plane, investigators said Friday.

National Transportation Safety Board Chairwoman Jennifer Homendy told reporters that the recording from the Black Hawk helicopter cockpit suggested an incomplete radio transmission may have left the crew without understanding how it should shift position just before the Jan. 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.

The helicopter pilots may have also missed part of another communication, when the tower said the jet was turning toward a different runway, she said.

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.

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.”

The collision was the 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.

William Waldock, professor of safety science at Embry-Riddle Aeronautical University, said stepped-on transmissions — where a pressed microphone key blocks incoming communication — is a well-known problem in aviation.

“It’s an old story and it’s one of the problems oftentimes with radio communications,” he said.

It’s unclear, though, if that led to the crash.

Retired airline pilot John Cox, CEO of the aviation safety consulting firm Safety Operating Systems, said the helicopter’s pilots had accepted responsibility to avoid the plane two minutes earlier when they asked for and received permission to maintain “visual separation” with the jet — allowing it to fly closer than otherwise may have been allowed if the pilots didn’t see the plane.

“At that moment, the helicopter becomes responsible for separation, period. He accepts the responsibility of staying clear of the other aircraft,” Cox said. If the helicopter pilots suspected they had missed any crucial information from the tower, they could have asked for it to be repeated.

Serious questions have yet to be answered about the helicopter’s altimeters.

The collision likely occurred at an altitude just under 300 feet (91 meters), as the plane descended toward the helicopter, which was well above its 200-foot (61-meter) 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 (91 meters), but the instructor pilot saying they were at 400 feet (122 meters), Homendy said.

“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 (85 meters), 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.

Waldock said the helicopter pilots, with their night vision goggles interfering with their peripheral vision, may have wrongly focused on a plane that took off just before the collision.

“If they did indeed lock onto that departing airplane and assume that’s the traffic they were supposed to be avoiding, they didn’t see the other airplane coming,” he said.

The jet also angled sharply upward in the last second before impact, Homendy said.

Waldock and Cox both saw that as a clear evasive maneuver by the American Airlines pilot.

“It’s a last ditch attempt to escape,” said Waldock.

The victims

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

The Army identified the crew as Capt. Rebecca M. Lobach of Durham, North Carolina; 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 he had dreamed of flying since he was 3.

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.