All 64 people aboard an American Airlines jet that collided with an Army helicopter were feared dead in what was likely to be the worst U.S. aviation disaster in almost a quarter century, officials said Thursday.

Over the next year or more, NTSB investigators will piece together how a passenger jet and Black Hawk military aircraft collided in Washington, D.C.

The National Transportation Safety Board (NTSB) said investigators were on scene of a crash that took place near Ronald Reagan Washington National Airport (DCA) Wednesday night. NTSB posted on the X platform that it launched a “go-team” to look into the incident involving a PSA Airlines Bombardier CRJ700 airplane