The investigation into a January midair collision that killed 67 people near Washington, D.C., revealed an alarming number of recent close calls just outside the nation’s capital.

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.