The last major collision of a commercial U.S. airline dates back to 2009, when a Colgan Air incident left 50 dead near Buffalo, New York. Federal regulators tightened safety requirements following the crash, including bolstering aircraft carrier inspection requirements and pilot training hours.

Questions, disbelief, and heartache as more is learned about the deadly collision between an American Airlines passenger jet and the army helicopter that collided at Ronald Reagan Washington National Airport.

A airplane and military helicopter collided in Washington, D.C., before plunging into the Potomac River. Here's who was on board, flight path and more.