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.

The board opened the three days of hearings by showing an animation and playing audio and video from the night of the collision, as well as questioning witnesses and investigators about how the Federal Aviation Administration and the Army may have contributed to nation’s deadliest plane crash since November 2001.

The National Transportation Safety Board said on Wednesday that testing showed faulty altitude data in U.S. Army helicopters like the one that collided with an American Airlines plane in Washington, D.