Sixty-four people aboard a commercial airliner died Wednesday night after it collided with a military helicopter midair near Reagan Washington National Airport. Both the American Eagle jet and Army Black Hawk are in the Potomac River.

Dozens of people are dead after a regional jet collided with an Army Black Hawk helicopter Wednesday night over Washington, D.C., officials said, the nation's first major commercial airline crash since 2009.

As to what may have gone wrong and caused an American Airlines commercial jet and a military helicopter to collide, we spoke with a former NTSB investigator and former Black Hawk helicopter pilot to weigh in on the subject.