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.

On the eve of the investigative hearings, Republican Sen. Ted Cruz introduced legislation called "The Rotor Act," which would require all aircraft, including military, to transmit ADSB location when flying -- a system that allows aircraft to transmit its location to other aircraft as well as to air traffic controllers.

The Army helicopter that collided with a plane over D.C. in January had incorrect altitude readings, contributing to the aircraft getting too close.