Japan Airlines flight JL687, a Boeing 737-846, encountered turbulence during the descent to Miyazaki Airport, Japan. One female passenger of age 60s hit her chest against the armrest of the seat and was seriously injured. The aircraft continued the flight and landed at the airport at 10:04. The passenger went hospital later, and was found her left 8th and 9th ribs fractured. She reported her injury to JAL on 23rd January. PROBABLE CAUSES The JTSB concludes that the probable cause of this accident was that the left side of the passenger most likely hit hard against the armrest of the seat, resulting in injury as the upper body of the passenger was swung to the left because the lateral acceleration changed due to the translational movement and yawing of the aircraft when the aircraft skimmed the cumulus clouds after the seat belt sign was turned on