One of my colleagues flew up from Nanning today. He was originally booked on an 8a flight, but that was cancelled last night because the airplane never left Shanghai.
He ended up on an afternoon flight in the end, and asked about the cancellation.
The stated reason was simultaneous drills in 7 cities: Nanjing, Beijing, Chengdu, Jinan, Lanzhou, Shenyang, Guangzhou. They also advised that these drills (some announced in advance and others not) will continue until September 3.
I'm thinking of postponing my flights next week (I can't imagine productivity is going to especially stellar next week anyway).