WASHINGTON, D.C. — The National Transportation Safety Board chairman called for immediate changes at Washington, D.C.'s Ronald Reagan Washington National Airport, saying the current helicopter routes around the airport "pose an intolerable risk to aviation safety."

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.

The National Transportation Safety Board has released their preliminary report into the deadly midair collision between an American Airlines flight and a U.S. Army Black Hawk helicopter over Washington,