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.

In the three years before the deadly collision between an Army helicopter and an American Airlines flight near Reagan National Airport, at least two other pilots reported near-misses with helicopters while landing at the airport,

An Army Black Hawk helicopter collided midair with an American Airlines flight from Wichita, Kansas, at Reagan National Airport on Wednesday.