Pan Am Flight 923 was a Douglas DC-4 operating from Seattle, Washington to Juneau, Alaska, which crashed into Tamgas Mountain on Annette Island, Alaska, on October 26, 1947. All 18 passengers and crew on board were killed. The crash was the worst in Alaskan commercial aviation at the time, as well as the first crash of a Pan Am four-engine aircraft. An investigation by the Civil Aeronautics Board (CAB, the precursor to the NTSB) was unable to determine probable cause and it remains unknown to this day.