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,

Investigators issued their preliminary report Tuesday in the probe into the devastating crash between an American Airlines plane and a U.S. Army Black Hawk helicopter.

Federal investigators recommended a ban on some helicopter flights Tuesday, after looking in the cause of the tragic collision between