What happened
While operating at flight level 220 during nighttime operations, the aircraft experienced significant vertical oscillations of approximately 500 feet, as observed by air traffic controllers at Salt Lake Center. Following these altitude fluctuations, the aircraft entered a descent and the transponder signal was lost. A subsequent analysis of the flight path indicated that the aircraft was performing a tight right-hand turn while descending.
Upon investigation of the debris, it was determined that the aircraft underwent a structural breakup in flight. The wreckage distribution indicated that the empennage and its related control surfaces detached from the airframe prior to the separation of the wings. Evidence from the crash site also showed that a fire occurred prior to impact, and the primary fuselage was consumed by a heavy post-crash fire.
Findings
Physical examination of the wreckage identified that the right elevator had separated due to negative overload. Additionally, both wings were found to have separated under negative loading conditions. While the structural failure was evident, investigators were unable to identify the initial event that triggered the altitude deviations and the descending turn.