Data from a cockpit voice recorder of the Black Hawk helicopter that collided with an airliner near Washington, D.C, last week suggests the crew was wearing night-vision goggles.

Now, the U.S. Army Corps of Engineers will focus on retrieving the mangled helicopter, a crucial component in federal authorities' probe as they look to confirm data related to its altitude at the time of the collision,

A key safety system was turned off in a US army helicopter when it crashed into an American Airlines flight last week, killing 67 people.