The Army goggles would have made it difficult to see the plane's colored lights, which might have helped the Black Hawk determine the plane's direction. The goggles also limited the pilots' peripheral vision as they flew near Ronald Reagan Washington National Airport.

The first of the National Transportation Safety Board’s three days of investigative hearings is underway to help determine what caused the deadly midair collision on January 29 between an Army helicopter on a training mission and American Airlines flight 5342 landing at Ronald Reagan Washington National Airport.

The acknowledgement came during the second day of testimony held to discuss the collision of a commercial plane and Army helicopter in January that killed 67 people.

The FAA plans more changes to helicopter routes near Reagan Airport to improve safety, after fatal mid-air collision in January.

Long-standing concerns about military helicopters flying in crowded airspace and worries over short staffing among federal aviation workers emerged Thursday as key factors in investigators' inquiry into the fatal midair crash between an Army helicopter and a commercial airliner earlier this year.

The board focused on air traffic control and heard it was common for pilots to ask to use visual separation — relying on eyesight — just as the Army Black Hawk’s pilot agreed to do the night of the crash.