Associated Air Transport Trip 1-6-6A

On January 7, 1953, a Curtiss C-46F Commando operating as Associated Air Transport Trip 1-6-6A crashed into terrain approximately 8 miles west of Fish Haven, Idaho, killing all on board. The plane had descended into an area of severe icing, causing ice to form on the wing, eventually crashing into the bottom of a ravine.

Accident
The flight departed Boeing Field at 12:50 AM MST, and proceeded en route to Cheyenne Airport. At 3:58 AM, the aircraft reported passing over Malad City, and estimated that it would reach Rock Springs at 4:45 AM. However, no further communications were received from the accident aircraft.

The aircraft was later found to have impacted several pine trees, slid down a ravine, and collided with the base of a hill on the other side of the ravine.

Aircraft
The Curtiss C-46F Commando was registered as N1648M (MSN 22395). It had first flown in 1945, and at the time of the accident, the aircraft had 1941 airframe hours.

Investigation
The investigation determined that, while flying near the mountains in between Malad City and Bear Lake, the aircraft involuntarily descended into an area of ice and turbulence, to avoid storm clouds. Ice began to form on the wings of the aircraft, which led to a decrease in aircraft performance and, eventually, the aircraft impacting a hill at the bottom of a ravine.

Causes
The investigators determined that the aircraft experienced severe turbulence and wing icing, which led to the aircraft's crash. However, the investigators were unable to determine the reason for the aircraft's descent into severe turbulence and icing conditions.