The 1955 Hawaii R6D-1 crash was an accident involving a Douglas R6D-1 Liftmaster of the United States Navy which crashed into a mountain peak in Hawaii on 22 March 1955, killing all 66 people on board. At the time, it was the worst crash involving any variant of the Douglas DC-6 airliner the second-worst aviation accident in U.S. history, and one of the worst air accidents anywhere in history, and it equalled the 6 October United Airlines Flight 409 crash as the deadliest air accident of 1955. It remains the worst air disaster in the history of Hawaii and the deadliest accident involving a heavier-than-air aircraft in the history of United States naval aviation.