Mongolian Airlines B737-800 Emergency Landing in France Due to Cabin Depressurization (EI-CSG)

Incident Overview and Flight History On 8 June 2016, a Boeing B737-800 with registration EI-CSG, operated by MIAT Mongolian Airlines, was conducting a scheduled passenger flight from Prague (PRG) to Seville. The aircraft departed Prague at 16:44 UTC. During the initial climb to approximately 11,200 feet, the crew observed the 'Auto fail' and 'Master caution' lights illuminate. Following the Quick Reference Handbook (QRH) procedures, the crew switched the pressurization system to the alternate mode, which temporarily resolved the warning. ## Emergency Descent and Landing While in straight-and-level flight at 35,000 feet, approximately 80 kilometers from Toulouse, France, the 'Auto fail' light illuminated again at 18:10:30 UTC. The crew subsequently switched the system to manual mode. The cabin pressure then decreased, and the cabin altitude reached 10,010 feet, triggering a cabin altitude warning. Determining that the cabin altitude was uncontrollable, the crew initiated an emergency descent and landed at Toulouse airport at 18:34:30 UTC. ## Personnel and Damage The aircraft was carrying 11 crew members and 183 passengers. No injuries were reported among the personnel on board, and the investigation found no damage to the aircraft or other property. The incident was investigated by the Air Accident Investigation Bureau of Mongolia following the transfer of jurisdiction from the French investigation authority (BEA).