Last month, an American Airlines passenger jet and an Army helicopter collided as the plane prepared to land at Washington D.C.’s Ronald Reagan National Airport.

Investigators revealed that the U.S. Army Black Hawk helicopter that collided with American Airlines Flight 5342 was flying about 100 feet higher than it should have been, and also stated the helicopter crew was warned about the incoming jet two times.

The National Transportation Safety Board provided an update on Friday into the investigation of the deadly Army Black Hawk helicopter and American Airlines flight collision.

LIVE: Watch the NTSB press conference in the video player above. The collision was the deadliest plane crash in the U.S. since 2001, when a jet slammed into a New York City neighborhood just after takeoff,