The deadly mid-air collision over Washington, D.C., has reignited concerns over air traffic congestion and safety risks at Ronald Reagan Washington National Airport, a tightly packed aviation hub that shares airspace with military and government flights.

The National Transportation Safety Board has interviewed the air-traffic controller who was working at the time of the midair collision, board member Todd Inman said, adding that the interviews have been ongoing throughout the day.

The staffing at the air control tower at Reagan National Airport was "not normal" when an American Airlines plane and Army helicopter collided on Wednesday night, a report shows.

Understaffed and overworked air traffic control crews have long been an issue at Ronald Reagan Washington National Airport, lawmakers say — another potential cause of the midair collision between a commercial jet and military helicopter over the Potomac River that killed 67 people Wednesday night in the nation’s deadliest air crash since 2001.

Sixty-seven people died in a collision between a Bombardier CRJ700 regional jet operated by PSA Airlines and a military Black Hawk helicopter.