The National Transportation Safety Board on Tuesday recommended that helicopter traffic be banned from a four-mile stretch over the Potomac River when flights are landing at Ronald Reagan National Airport.

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,