Investigation Summary
Flight 557 was a domestic scheduled service from Ulaanbaatar to Moron. During the approach, the flight crew elected to transition to visual flight, believing the visibility was sufficient for the maneuver. However, the region was experiencing marginal weather conditions with poor visibility. While descending toward the airport, the pilots misjudged their position and began their final descent significantly earlier than prescribed by the approach procedures. The aircraft struck the side of Choho Geologloh Uul, a mountain located approximately 12 kilometers (7 miles) from the airport. The impact destroyed the aircraft, killing all six crew members and 36 passengers. A single male passenger, Ulziibayar Sanjaa, was recovered as the sole survivor with serious injuries.
Final Conclusions
The investigation concluded that the primary cause of the accident was Controlled Flight Into Terrain (CFIT) resulting from pilot error. The crew's decision to initiate a premature descent below the minimum safe altitude in an area of high terrain was the direct cause of the impact. Contributing factors included a lack of cockpit discipline and the decision to continue a visual approach despite marginal visibility and poor weather conditions.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Visual Flight Rules (VFR)
The crew elected to use visual references for navigation and terrain avoidance rather than relying solely on instruments, which proved fatal when visibility was insufficient to clear the mountain.
Altimeter
While not cited as malfunctioning, the crew failed to maintain the minimum prescribed altitude for the approach segment, leading to the premature descent.
Interesting Facts
- 01The accident is the deadliest aviation disaster in the history of Mongolia.
- 02The aircraft was carrying 37 passengers and 6 crew members; 36 passengers and all 6 crew members were killed.
- 03The aircraft was manufactured in 1975 and had the serial number 57310103.
- 04The sole survivor was a passenger named Ulziibayar Sanjaa.
- 05The crash site was located approximately 12 kilometers (7 miles) from the destination airport.
- 06The aircraft was originally allocated the registration MT-1008, but it was not in use at the time of the crash.
Safety Actions & Advisories
Fleet Modernization and Safety Targets
Source ↗Following a series of fatal accidents in the 1990s, MIAT Mongolian Airlines initiated a safety improvement program targeting pilot discipline and the modernization of its fleet to replace aging Soviet-era aircraft.