Civil aviation flights in northern China will be allowed in military-controlled airspace during thunderstorms in the latest move to reduce flight delays.

A new regulation, enacted on Tuesday, from the North China Air Traffic Management Bureau under the Civil Aviation Administration of China and the People's Liberation Army air force opened 25 temporary flight paths and one temporary airspace for civil aviation flights in northern China during thunderstorms.

The move, another major sign of cooperation between the civil aviation authority and the air force, is expected to reduce flight delays at Beijing Capital International Airport, whose flights are frequently affected by thunderstorms in summer and fall.

According to the new regulation, the bureau will devise the detour flight paths to avoid thunderstorms and submit the request to the air force one hour before the flight. The military will reply to the request 30 minutes before the flight.

The new flight paths will cover airports in five provincial areas, including the municipalities of Beijing and Tianjin; Shanxi and Hebei provinces; and the Inner Mongolia autonomous region.

The regulation also covers the plan in which flights are allowed to take off and land when thunderstorms end.

Wen Xuezheng, chief of the North China Air Traffic Management Bureau, said the new regulation will significantly reduce flight delays in northern China in summer and increase air traffic capacity during harsh weather.

Poor weather accounts for about 20 percent of flight delays in China, the civil aviation authority said in 2011.

Previously, when a thunderstorm lay on a flight route between two cities, the flight had to be delayed because the flight could not detour through controlled airspace.

"The new regulation will enable flights to take detours in the controlled area after requests and thus could reduced the delays," said Yan Xiaodong, the bureau's chief engineer. He expects the flight delays at Beijing's airport this summer will be significantly less than they were last summer

Meanwhile, the new regulation will also significantly reduce the flight mileage during storms and thus reduce airlines' costs.

The new regulation also is expected to prevent the inconvenience to passengers when they are forced to use other airports when thunderstorms delay flights at the Beijing airport. Flights with enough fuel could circle western Beijing until the storms dissipate and the planes can land.

xuwei@chinadaily.com.cn