The heaviest fog to affect southwest China's Chongqing Municipality so far this winter has delayed more than 200 flights and led to the cancellation of another 10, affecting about 15,000 passengers, Xinhua reported. The fog, which the municipal observatory said reduced average visibility to less than 100 meters in Chongqing, virtually closed Jiangbei International Airport during Saturday morning, with no departures or arrivals before 11:30 a.m., airport authorities said. Flights began to resume at midday, but further delays were reported in the afternoon due to the backlog of flights. At least three international flights, bound for London, Frankfurt and Nagoya, were delayed for an average of four hours, according to the website of Chongqing Airport Group. The heavy fog closed down all nine expressways in Chongqing, the expressway administration told Xinhua. Visibility was only five meters in some areas between Friday night and Saturday morning, the observatory said. It said the foggy weather, which started on Friday, will persist through Monday.