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

It’s been more than a month since an American Airlines plane and a U.S. Black Hawk helicopter collided and plunged into the Potomac River, killing 67 people. On Tuesday, the National Transportation Safety Board (NTSB) will hold a media briefing to share the latest details of its investigation.

The Federal Aviation Administration has imposed permanent restrictions on non-essential helicopter operations around the Washington, D.C., airport where an Army chopper collided with a commercial jet