Department of Defense Secretary Pete Hegseth has said that the pilots aboard the U.S. Army helicopter that collided with an American Airlines plane were wearing night vision goggles — but an expert says that could have hurt their ability to see other aircraft.

The American Airlines plane crashed into a U.S. Army Black Hawk helicopter over the Potomac River near the Ronald Reagan Washington National Airport on the evening of Wednesday, Jan. 29. At least 29 bodies had been recovered as of Thursday at noon, with all 64 people aboard believed to be dead, Washington, D.C. Fire and EMS Chief John A. Donnelly said.

The U.S. Army Black Hawk helicopter had three soldiers aboard, who are all believed to be dead.

On Thursday morning, Hegseth said in a video message on X, “It was a fairly experienced crew that was doing a required annual night evaluation.” He added, “They did have night vision goggles.”

Night vision goggles are designed to enhance operational safety and improve the pilot’s ability to see and avoid obstructions at night, per the FAA.

However, an active-duty U.S. Army pilot tells PEOPLE that the goggles may have actually hindered the pilots’ efforts to avert the crash.

“Those goggles are designed for situations where the only light is moonlight or starlight. If you already have a lot of things moving around and blinking, it could throw things off,” the pilot tells PEOPLE. “They could make it harder to see what’s going on in the sky.”

An aviation expert, along with the Army pilot, tells PEOPLE that Reagan National Airport can be especially difficult to fly into.

“You can almost think about there [are] lanes in the sky that you need to stay to. And in D.C., those lanes are very narrow because we have a lot of buildings that are close by the airport,” Laurie Garrow, an aviation expert at Georgia Tech University, tells PEOPLE.

“So it’s very common that aircraft are going on the Potomac,” she says, “but that probably also creates more congestion and things to manage, particularly if you’re mixing commercial and military operations.”

Her thoughts echoed those of the Army pilot who spoke with PEOPLE.

“Flying into that airspace, it is super busy. There is so much moving around. There’s darkness, blinking lights, and a lot of movement,” he says. “In that environment, the night vision goggles would possibly make it harder to read the sky.”

The FAA and National Transportation Safety Board are investigating the crash, which is now the deadliest U.S. aircraft incident since 2001, when an American Airlines flight crashed into a harbor in New York City and killed all 260 people on board.