Flight instruments probably led the Black Hawk crew to believe the helicopter was lower than it actually was before the collision with a commercial airplane on Jan. 29.

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.