Adds Duffy comments in paragraphs 1-4

By David Shepardson

WASHINGTON, March 11 (Reuters) - U.S. Transportation Secretary Sean Duffy on Tuesday said the agency will make permanent restrictions to prevent helicopters from flying near Washington Reagan National Airport when two lesser-used runways are operational, a move that followed a mid-air collision in January that killed 67 people.

Duffy said he was responding to an urgent safety recommendation from the National Transportation Safety Board, which had cited the "risk of mid-air collisions between helicopters," according to a letter to the Federal Aviation Administration first reported by Reuters.

Duffy said he will also adopt another NTSB recommendation that the FAA create an alternate route that can be used by helicopters when the two secondary runways at Reagan National are in use.

NTSB Chair Jennifer Homendy said at a press conference the prior rules for the two lesser-used runways at Reagan National created "an intolerable risk to aviation safety," saying there could be as little as 75 feet (23 meters) separating a helicopter and plane approaching one of those runways.

In the aftermath of the January 29 crash between an American Airlines passenger jet and a Black Hawk military helicopter over the Potomac River in Washington, D.C., the FAA temporarily barred most helicopters near the airport - located in Arlington, Virginia - until it could review the NTSB's initial findings.

The Black Hawk, carrying a crew of three, collided with the American Airlines jet, which was carrying 64 passengers and crew members, with the wreckage plunging into the river. There were no survivors.

After the crash, the FAA imposed an interim restriction that prevented civilian planes from being in the same area when police, medical or presidential transportation helicopters must use the airspace around Reagan National.

The NTSB recommendation would allow helicopters to fly when airplanes were using Runway 1 at Reagan National, which handles about 90% of the airport's traffic.

Airlines for America, a group representing American Airlines and other U.S. carriers, last week urged the FAA to permanently reduce helicopter traffic around the airport. The group called on the FAA to suspend some nearby helicopter routes with limited exceptions for essential military or medical emergencies.

The airline group wants the FAA to evaluate whether helicopter routes that may conflict with airplane flights at Reagan could be moved farther away from commercial traffic. It also has urged the FAA to conduct an immediate review of air traffic near large airports.

The FAA is conducting a review of helicopter routes near other airports.

Duffy has called for ending non-essential military helicopter flights near Reagan National.

"If we have generals who are flying in helicopters for convenience through this airspace, that's not acceptable. Get a damn Suburban and drive - you don't need to take a helicopter," he said.

(Reporting by David Shepardson; Editing by Chizu Nomiyama, Paul Simao and Bill Berkrot)

((David.Shepardson@thomsonreuters.com; 2028988324;))