NTSB hearings and documents revealed failures by the Army and FAA in the Jan. 29 crash of an American Airlines jet and an Army Black Hawk that killed 67.

Three days of investigative hearings on the deadly midair collision over Washington in January began Wednesday, aiming to reveal new insights into what caused the crash between a passenger plane and an Army helicopter that killed 67 people.

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.