一伦敦飞北京航班出现故障备降，国航通报

Group 1 - The flight CA856 from London to Beijing experienced a mechanical failure during the flight, leading to a safe emergency landing as per protocol [1] - To ensure passenger service and support, Air China dispatched another aircraft to the emergency landing airport to carry out subsequent flight tasks [1] - The replacement flight successfully arrived at Beijing Capital International Airport at 4:40 AM on August 27 [1]