Washington DC - The US aviation regulator said Friday it has ordered stricter safety around Washington's Ronald Reagan airport after a devastating collision between a passenger jet and a military helicopter.

Helicopter traffic will be restricted around the airport, where an American Eagle airliner hit a military Black Hawk on January 29, killing 67 people.

The Federal Aviation Administration also closed part of a corridor near Ronald Reagan National Airport that the military helicopter was using when it collided with the Bombardier CRJ-700 jet. Both fell into the freezing Potomac River.

The route was just 75 feet from the corridor used by the American Eagle jet as it came in to land.

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The National Transportation Safety Board has already warned of a risk of more collisions around the airport unless helicopter access was cut.

The FAA said it was taking "a series of steps to improve safety" around Reagan airport following NTSB recommendations.

These included "permanently restricting non-essential helicopter operations" around the airport and "eliminating helicopter and fixed-wing mixed traffic", the FAA statement said.

Reagan airport is in a heavily urbanized zone close to the Defense Department headquarters, and the FAA said alternative routes would be found for helicopters.

"If a helicopter must fly through the airspace on an urgent mission, such as lifesaving medical, priority law enforcement, or presidential transport, the FAA will keep them specific distances away from airplanes."

Two runways will be closed when helicopters on urgent missions are near the airport, the agency added.

NTSB head Jennifer Homendy said this week that the distances between helicopter traffic and commercial airliners around the airport posed "an intolerable risk to aviation safety".

The investigation into the January 29 disaster is not complete but has already highlighted different versions over the altitude, the military helicopter was flying at, and communication difficulties between the crew and the control tower and the looming American Eagle jet.