National Transportation Safety Board investigators issued a pair of “urgent” safety recommendations for helicopter paths on Tuesday as part of their preliminary report into the deadly midair collision over the Potomac River in January.

Helicopters should be barred from a four-mile stretch over the Potomac River when flights are landing on Reagan National Airport’s Runway 33, National Transportation Safety Board Chair Jennifer Homendy said as the NTSB unveiled “urgent safety recommendations” after the deadly mid-air collision in January.

Helicopters should not be allowed to travel over a four-mile stretch over the Potomac River following the deadly air collision near Washington in January, according to urgent safety