“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.

The National Transportation Safety Board plans to release the preliminary report on the deadly collision involving American Airlines Flight 5342 en route from Wichita to Washington, D.C.'s Ronald Reagan National Airport and an Army Black Hawk helicopter.

Federal investigators looking into the cause of the January collision between a passenger jet and an Army helicopter near Washington, D.C., that killed