Investigators probing the January midair collision of a passenger plane and an Army helicopter over Washington that killed 67 people found the chopper was flying higher than it should have been and its altitude readings were inaccurate.

A National Transportation Safety Board hearing revealed that the U.S. Army was aware of altitude discrepancies on Black Hawk helicopters.

Investigators have found that a helicopter involved in a deadly crash with a passenger plane over Washington was flying above its height limit.