The U.S. National Transportation Safety Board (NTSB) has announced that the landing gear failure involving an Alaska Airlines Boeing 737-800 in August 2023 was caused by improper maintenance procedures carried out in previous years. According to the final accident report published on 27 May 2025, investigations revealed that a fatigue crack in the main landing gear (MLG) component caused the gear to collapse during landing.
Grinding Error in July 2018 Set the Stage for Disaster
According to the NTSB’s detailed analysis, the rear trunnion pin of the aircraft’s left main landing gear was “excessively ground” during maintenance in July 2018. This operation damaged the base metal of the part and eventually led to the development of a fatigue crack. During the aircraft’s landing, the crack expanded, resulting in the pin breaking and the gear collapsing.
The aircraft involved in the incident experienced a collapse of its left landing gear while landing at John Wayne–Orange County Airport (SNA) in California. All 106 passengers and 6 crew members on board escaped without injury, but the left wing sustained significant structural damage. The aircraft was returned to service after undergoing necessary repairs.
Hard Landing Claims Proven Unfounded
On the night of the incident, local weather conditions, SNA’s short runway (5,700 ft), and noise abatement procedures initially raised suspicions of a hard landing. However, the NTSB determined that the aircraft experienced a vertical acceleration of approximately 1.7g upon touchdown—below the threshold for a hard landing.
Sunvair Reviews Maintenance Process
The NTSB report stated that the landing gear in question had been overhauled in 2018 by Valencia, California-based MRO firm Sunvair. Microscopic and metallographic examinations revealed that the crack had formed in an area exposed to high temperatures generated during the grinding process.
The NTSB emphasised that this condition was due to the metal overheating and softening during grinding, consistent with tempering damage. The report also noted that microstructural degradation and surface contrasts in the affected area supported this finding.
Following the incident, Sunvair reportedly reassessed its trunnion pin overhaul procedure and integrated an additional inspection step into the repair process.
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