Federal investigators probing January’s fatal air collision near Ronald Reagan Washington National Airport have called for restrictions on military helicopters to make the area safer for commercial passengers.

The Federal Aviation Administration says helicopters will be permanently banned from flying near Washington, D.C.’s airport on the route where an airliner and an Army helicopter collided in midair.

The NTSB’s preliminary report on the Jan. 29 crash that killed 67 people current helicopter routes allowed around the airport are an ‘intolerable risk to aviation safety.’