The U.S. Army helicopter that collided with an passenger jet near Washington, D.C., had an advanced surveillance system turned off.

Families and friends of those who lost loved ones in the deadly American Airlines and Army helicopter collision are sharing tributes online in memory of the crash victims.

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.