Federal investigators revealed Wednesday that the Black Hawk helicopter involved in the deadly DCA crash may have misreported its altitude by more than 100 feet, a flaw the Army had long known about but never formally documented.

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

The National Transportation Safety Board said on Wednesday that testing showed faulty altitude data in U.S. Army helicopters like the one that collided with an American Airlines plane on January 29, killing 67 near Ronald Reagan Washington National Airport.