Departure and Route Modification
On the morning of the accident, a four-engine cargo aircraft departed from Alameda Naval Air Station, California, en route to Wilmington with an intermediate stop in Indianapolis. The flight was conducted on behalf of the US Air Force. While cruising over Colorado, the crew modified the planned route to avoid a thunderstorm area.
In-Flight Structural Failure
Several minutes after the route change, while the aircraft was cruising in better weather conditions, the left wing detached at section 162. The aircraft immediately experienced sharp rolling and yawing. Subsequently, the left wing completely failed, and the right wing failed outboard of the number 4 engine.
Loss of Control and Crash
Having lost both wings, the aircraft entered an uncontrolled dive and crashed into an open field. All four crew members were killed in the accident.
Probable Cause
The official investigation determined the probable cause to be: The undiscovered, preexisting fatigue cracks, which reduced the strength of the left wing to the degree that it failed as a result of positive aerodynamic loads created by moderate turbulence.