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 so far have highlighted several factors that may have contributed to the collision, which left 67 people dead.

Tuesday was day two of a three-day hearing on the deadly plane crash at Reagan Airport that took the lives of 67 people in January.