What happened
On the morning of the accident, an aircraft departed from Helena using Runway 29 at 07:53 local time. The flight plan, which had been updated prior to departure, intended for the flight to climb to 10,500 feet MSL under instrument flight rules. The route was planned via Amber Airway number 2 toward the Whitehall (Montana) Range Station, continuing to Butte Airport via Red Airway number 2.
Shortly after takeoff, the pilot performed a climbing right turn to pass over the station while traveling south. At 08:01, the crew notified Helena that they had reached their assigned cruising altitude. By 08:14, the flight contacted Butte Radio to report that they had passed the Whitehall Range Station at 08:11 and were beginning their descent. During this exchange, controllers provided an altimeter setting of 29.97 and updated the crew on local wind conditions and weather bureau reports regarding low ceilings to the east and north.
The flight reported having vertical visibility at 10,500 feet, which served as the final radio communication from the aircraft. After several unsuccessful attempts to re-establish contact, a search operation was launched. The wreckage was discovered the following morning by a search aircraft at approximately 09:00. The debris field was located in a wooded, snow-covered area. The accident resulted in 21 fatalities.
Findings
Investigations into the crash determined that the aircraft struck a mountain at an elevation of roughly 8,250 feet while traveling on a magnetic heading of approximately 290 degrees. The investigation concluded that the primary cause was the pilot's failure to follow the established instrument approach procedure for Butte Airport. Additionally, the accident took place during a local snowstorm characterized by fluctuating visibility and ceiling heights.