The NTSB concluded three days of investigative hearings into the collision between an Army helicopter and a passenger plane that killed 67.

The National Transportation Safety Board on Wednesday opened a three-day hearing into the deadly midair collision over Washington, D.C., that killed all 67 aboard a passenger jet and military helicopter.

NTSB investigators found Friday that the aircraft involved in the mid-air collision over DCA lacked certain collision avoidance systems