What happened
On October 28, 1960, a Douglas C-54A-DC, registration N 48762, was operating as Northwest Airlines Flight 104 when it crashed approximately 13 nautical miles northwest of the Missoula, Montana Airport. The aircraft had departed from Spokane, Washington, under an instrument flight plan. During the flight, radio communications remained routine, and the crew reported no operational difficulties while remaining on schedule.
As the aircraft proceeded toward its destination, it was seen by observers on the ground traveling through the Clark Fork Valley. At this stage, the engines were functioning, and the plane appeared to be descending in preparation for an approach. However, weather conditions were deteriorating; light snow showers had reduced visibility, and heavy cloud cover obscured the surrounding mountain peaks.
During its descent into the valley, the aircraft entered a sharp left bank. The pilot attempted to raise the nose of the plane to climb out through a different valley, but the aircraft lost altitude and continued to sink. The plane eventually rolled to the left and struck the ground in an inverted position. The accident resulted in 12 fatalities, including the pilot, the first officer, two flight attendants, and eight passengers.
Findings
Investigations concluded that the primary factor in the accident was the pilot's decision to attempt a visual flight rules approach despite being under instrument flight rules conditions.