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 carrying night vision goggles — but an expert says that could have hurt their ability to see other aircraft.

The incident comes a week after an American Eagle regional jet collided with an Army Black Hawk helicopter over the Potomac River near Washington D.C. The reasons as to why the plane was interrupted in its journeys over the past month is unknown

Investigators have yet to determine whether the crew of an Army helicopter was wearing the devices when the Black Hawk crashed into a civilian airliner last week.