The NTSB concluded three days of investigative hearings into the collision between an Army helicopter and a passenger plane that killed 67.

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.

The National Transportation Safety Board questioned witnesses Friday on collision avoidance technology and organizational systems to manage risk. It is the third and final day of investigative hearings probing January’s midair collision between a US Army Black Hawk helicopter and an American Airlines regional jet,