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,

Data from air traffic control radar showed the military chopper was flying at 300 feet on the air traffic control display at the time of the fiery crash, according to the NTSB.