Tragic Army Black Hawk helicopter collision kills 9 in Kentucky training mission.

Two US Army Black Hawk helicopters collided during a routine nighttime training mission over Kentucky's Trigg County, killing all nine soldiers on board. The cause of the crash is unknown, and an aircraft safety investigations team from Fort Rucker in Alabama will review data from onboard computers. The HH-60 Black Hawk is a variant designed for air assaults and medical evacuations. The crash is one of the deadliest training accidents in recent years, and Fort Campbell is one of the largest military bases in the US.