The NTSB said that the long-established route followed by helicopters, referred to in the report as Route 4, is fraught with danger. "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 midair collision,

Federal investigators looking for the cause of the January collision between a passenger jet and an Army helicopter near Washington, D.C., that killed 67 people are recommending a ban on some helicopter flights.