“We’ve determined that the existing separation distances between helicopter traffic operating on Route 4 and aircraft landing on Runway 33 are insufficient and pose an intolerable risk to aviation safety by increasing the chances of a mid-air collision at DCA,” NTSB Chair Jennifer Homendy said during a news conference.

Current airport flight safety practices create an "intolerable safety risk" that could be eliminated by changing allowed separation distances between helicopters and airplanes, federal officials say.