During the hearings, the NTSB was told that the Army helicopter never heard the command from the air traffic controller to "pass behind the CRJ" as the transmission was stepped on. It was also revealed that the plane's pilots were not warned by the controller that there was a helicopter nearby or cleared to fly near the helicopter.

Investigators have found that a helicopter involved in a deadly crash with a passenger plane over Washington was flying above its height limit. The helicopter's altitude-measuring instrument was also inaccurate.

Loved ones of Washington, D.C., plane crash victims wore photos of their late friends and family members as they attended the latest hearing about the fatal collision.

Last week, the NTSB held three days of hearings looking into what led up to the fatal crash between a plane and a helicopter in January.