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.

The Black Hawk was trying to land at the Pentagon’s heliport, bringing it close to a pair of airliners, according to the Federal Aviation Administration.

The National Transportation Safety Board is now investigating the aborted landings of two commercial flights approaching Reagan National Airport on Thursday as a U.S. Army Black Hawk helicopter was approaching the Pentagon nearby.