Investigation Summary
Flight 409 was running 83 minutes late when it departed Denver, having originally left New York 71 minutes behind schedule. The assigned route was designed to safely clear the Continental Divide at 10,000 feet, but the aircraft impacted the mountain at 11,570 feet, just 60 feet below the summit. The recovery effort was one of the most difficult in aviation history, requiring specialized mountaineers and a 900-foot rope-and-pulley system to lower remains down the cliff face. Due to the extreme terrain, Civil Aeronautics Board (CAB) investigators could not reach the primary impact point, relying instead on wreckage that had tumbled down the slope. Following the recovery, the military attempted to destroy the remaining wreckage using recoilless rifles and explosives to prevent curiosity seekers from attempting the dangerous climb.
Final Conclusions
The CAB determined the probable cause was the pilot's decision to deviate from the planned route for reasons that could not be determined. While theories regarding faulty altimeters, downdrafts, or carbon monoxide poisoning from the cabin heater were explored, no conclusive evidence supported them. The accident, along with other high-profile crashes of the era, served as a primary catalyst for the U.S. Congress to mandate expanded civil aviation radar coverage and modernized safety procedures.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Cabin Heater
Speculated as a source of carbon monoxide that could have incapacitated the crew, though this was never proven.
Altimeter
Investigated for potential inaccuracies that might have led the crew to believe they were at a safe altitude.
Interesting Facts
- 01The accident was the deadliest in U.S. commercial aviation history until the 1956 Grand Canyon mid-air collision.
- 02The aircraft struck the mountain approximately 60 feet below the crest according to the CAB, though some local accounts place the impact as close as 25 feet from the top.
- 03The crash site was located 20 miles west of the assigned V-4 airway route.
- 04Investigators found the aircraft was in a nose-up attitude at a low airspeed, suggesting a last-moment climb attempt.
- 05The recovery required a temporary morgue to be established at a nearby university science camp.
Safety Actions & Advisories
Expansion of Radar Coverage
The accident highlighted the lack of civil aviation radar in mountainous regions, leading to Congressional action to increase radar infrastructure.
Route Adherence Procedures
The crash reinforced the dangers of unauthorized 'short cuts' and led to stricter enforcement of flight path adherence for commercial operators.
Known Controversies & Unanswered Questions
Method of Wreckage Destruction
Reference ↗While many sources claim napalm was used by military jets to destroy the wreckage, other accounts state the cliff was mined with explosives in a controlled, non-publicized operation in 1956.