What happened
On August 27, 2018, an Airbus A320-214, registered JA14VA, operated by Vanilla Air Inc., was en route from Kansai International Airport to Amami Airport. While cruising at 30,000 feet over the sea approximately 45 km east of Miyazaki Airport, the aircraft experienced a sudden, single instance of vertical shaking.
At the time of the disturbance, a Boeing 747-40 and was flying approximately 13.3 nautical miles ahead of the aircraft at a higher altitude. The sudden vertical acceleration, which fluctuated between +0.19 G and +1.39 G, caused a flight attendant working in the aft galley to lose her balance. Unable to secure herself, she fell and struck her coccyx against the floor. Although the crew initially believed the event was merely light turbulence, the flight attendant later sought medical attention when persistent pain led to a diagnosis of a coccygeal fracture.