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.

Federal investigators have launched a probe after two flights aborted landings at Reagan Washington National Airport on Thursday because a U.S. Army Black Hawk helicopter too close.The Federal Aviation Administration said on Friday that air traffic control told Delta Air Lines Flight 1671,