BEIJING (AP) — China’s airline regulator has warned travelers to expect flight delays at 12 airports through mid-August, and an airport employee says military exercises are the reason.

The Civil Aviation Administration of China said Tuesday the airports affected include Shanghai, Nanjing, Hangzhou, Zhengzhou and Qingdao.

The disruptions began July 20 and are due to last through Aug. 15. The regulator cited unspecified exercises, but an airport employee reached by phone in one of the cities, Lianyungang, said the delays were due to military exercises.

The employee refused to give his name.