What we know about the deadly air crash between a passenger jet and a U.S. Army helicopter / What is known about the deadly air crash between a passenger jet and a US Army helicopter / What is known about the deadly January air crash between a passenger jet and US Army helicopter / What to know about the military helicopter involved in crash near DC / Army helicopter was alerted to plane's presence two minutes before collision / What we know about the Washington midair collision of an army helicopter and airliner / New details emerge about military helicopter involved in midair collision / Plane collides with military helicopter in Washington DC / What we know about Army helicopter, regional plane crash / Video appears to show American Airlines flight's collision with a US Army helicopter near DC