The Black Hawk that collided with an American Airlines jet in January may not have had accurate altitude readings, investigators said.

The National Transportation Safety Board is examining "bad data" the crew of an Army Black Hawk helicopter may have relied upon prior to their deadly crash with a passenger jet outside Washington D.C.

The NTSB is turning the focus of its investigation into the Jan. 29 collision on what the Black Hawk pilots could see and hear.

Black Hawk pilots may not have heard a critical directive from air traffic control to fly behind the American Airlines plane in the seconds before it collided with the jet, and may have had “bad data” on the altitude they were flying at,