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.

A small aircraft is down in the Potomac River near Ronald Reagan Washington National Airport and fireboats were on the scene, the Washington fire department said. The airport said late on Wednesday that all takeoffs and landings were halted at the airport as emergency personnel responded to an aircraft incident.

Hearing that just one air traffic controller was monitoring both planes and helicopters has left many to wonder how common such a situation is.