DALLAS — Investigators from the National Transportation Safety Board will likely be studying three main elements as they try to pinpoint the cause of the mid-air collision between American Airlines Flight 5342 and the U.S. Army helicopter on Wednesday night.

Ronald Reagan Washington National Airport (DCA) has canceled most flights and delayed some after a plane crashed midair into a helicopter as it was preparing to land. The airport announced that all flights have been halted but terminals are still open in the aftermath of the crash between American Airlines flight 5342 and a military Black Hawk helicopter over the Potomac River.