What happened
On the night of June 29, 1951, a Douglas DC-6 operated by United Airlines departed San Francisco for Chicago, with scheduled stops including Oakland, Salt Lake City, and Denver. After completing its stop in Salt Lake City, the aircraft departed at 00:11 on June 30, running approximately 26 minutes behind schedule due to the loading of large cargo items. At the time of departure, the aircraft's weight was recorded at 78,597 pounds, which remained within its maximum takeoff weight limits.
The flight was operating under instrument flight rules (IFR) via a specific airway structure, intended to cruise at 15,000 feet. The aircraft carried a total of 50 fatalities, comprising five crew members and 45 passengers, including one infant. After passing over Rock Springs, Wyoming, the flight proceeded normally until it reached the vicinity of Cheyenne, Wyoming. At 01:47, the crew reported passing the Silver Crown fan marker and requested permission to descend to a lower altitude. Air Traffic Control issued a new clearance to descend to 8,500 feet after passing the Cheyenne intersection.
At 01:56, the flight reported that it had successfully reached the assigned altitude of 8,500 feet. Following this transmission, all communication with the aircraft ceased. After the Denver Control Tower was unable to re-establish contact, investigations revealed that the aircraft had crashed into Mt Crystal, located approximately 18 miles west-southwest of Fort Collins, Colorado.
Findings
Investigation into the accident determined that the flight failed to adhere to its assigned route after passing through Cheyenne. The aircraft drifted beyond the boundaries of its designated airway, which ultimately led to the aircraft striking mountainous terrain.