A China Eastern Airlines Airbus A321-200, performing flight from Qingdao to Guangzhou (China), automatically released passenger oxygen masks due to unknown circumstances.

• Aircraft was enroute at 10400 meters (FL341) about 140nm northeast of Nanchang (China) when the passenger oxygen masks were automatically released, cabin pressure and all other indications remained normal however.
• The crew decided to divert to Nanchang, performed a precautionary descent to 3000 meters (9800 feet) and landed safely in Nanchang about 30 minutes after leaving 10400 meters.
• A replacement Airbus A321-200 registration B-6642 reached Guangzhou with a delay of 3 hours.