If changes aren't made, that near-miss becomes a mid-air collision,” one aviation safety expert said. “Unfortunately, that's what we had last night.”

Questions remain over the mid-air collision between a jet, which was carrying 64 people, including the crew, and a military helicopter carrying three soldiers

There is at least one casualty after a helicopter crash at a major airport tonight. All runways have been shutdown and all departures and landings have been halted at the DCA Ronald Reagan Washington National Airport.