The Jan. 29 collision over the Potomac River in Washington, DC — which preliminary reports have blamed on the military Black Hawk flying too high — was the deadliest US air disaster since 2001, and caused officials to change the flight path of helicopters near the airport.

A ‘New York Times’ investigation into the Jan. 29 midair collision between an American Airlines passenger jet and a U.S. Army Black Hawk helicopter found that the captain who was flying the military aircraft was not suffering from any medical impairment.