Ronald Reagan Washington National Airport (DCA) remained shut down on Thursday morning. Ronald Reagan Washington National Airport (DCA) remained shut down on Thursday morning after an American Airlines regional jet fatally collided mid-air with a military helicopter just outside the airport.

St. Paul International Airport and Washington D.C.'s Reagan National Airport have been canceled following the deadly collision between a passenger plane and an Army helicopter over the Potomac River on Wednesday night.

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.”