Airspace controls that have disrupted the travel plans of thousands of air passengers traveling to and from Shanghai since Nov. 20 will end at midnight on Nov. 24, according to the General Administration of Civil Aviation of China (CAAC).

"The controls will be removed on Nov. 25," said Li Jingao, an official with CAAC East China Air Traffic Management Bureau based in Shanghai.

The bureau continued to refuse to divulge the reason for the imposition of the controls.

Shanghai Airport Authority said on its website at least 40 flights were delayed at its two airports, Pudong and Hongqiao, on Nov. 23, including flights bound for Hong Kong, Harbin, Dalian and Chongqing.

Li said the situation was "much better" than the previous two days, but it would still take a day or two for flights to return to normal.

He said the current delays were mainly due to a knock-on effect from the past few days. "More flights are departing now to make up for the previous delays and this has increased pressure on the airports that are already operating at full capacity."

More than 150 flights were delayed in Shanghai and about 7,000 passengers were affected during the first two days of the airspace controls. Most flights were bound for domestic destinations including Guangzhou, Xiamen, Shenzhen, Beijing and Dalian.

Shanghai Airlines Co. said some of its flights were delayed for nearly six hours on Nov. 21.

Sources at the Baiyuan airport in Guangzhou, where 1,600 passengers suffered delays on Nov. 20, said several flights were still affected, but only for brief periods, with no large-scale passenger delays.