Aviation authorities confirmed Tuesday that passengers should expect considerable flight delays during the next month at 12 airports in Eastern and Central China due to "air traffic control" issues.

Due to frequent drills on the part of "other airspace users," widespread flight delays began on Sunday and are expected to last until August 15, a total of 26 days, said the Civil Aviation Administration of China (CAAC), according to China National Radio (CNR).

The affected airports include Hongqiao and Pudong international airports in Shanghai, as well as airports in major Chinese cities such as Nanjing, Hangzhou, Hefei, Ji'nan, Wuxi, Ningbo, Qingdao, Lianyungang, Zhengzhou and Wuhan.

Airlines have been required to reduce the number of flights departing from these airports, said the CNR report.

Although the notice did not specify the "other users," many believe that the "air traffic control" issues may in fact be caused by military drills. According to Li Jiaxiang, head of the CAAC, the civil aviation has jurisdiction over only 20 percent of China's airspace, Phoenix TV reported.

It is rare for air traffic control issues to cause delays of this duration across such a wide area.

The People's Daily reported earlier that China has launched a three-month live-fire drill for army units across six major Military Area Commands, including Nanjing, Ji'nan, Chengdu and Guangzhou, on July 15.

The drills have mobilized artillery, long-range rocket projectile and air defense units.

The authorities have not released any information on the question of whether these massive drills are the cause of the flight delays.

Widespread flight delays and cancellations in Shanghai's two airports last week, also due to air traffic control issues, triggered numerous complaints from passengers.