A thick fog over most of north China yesterday shut down flights at Beijing Capital International Airport and closed three main expressways, stranding thousands of travellers. The fog, which descended on Monday, cut visibility to 100 metres over much of north and northeast China. It also prompted a pollution advisory to be issued in the capital. Visibility was up to about 200 metres yesterday, according to the Beijing Weather Observatory. An airport authority spokesman and a representative of Air China said at noon that no flights had yet taken off. The airport closed on Monday night, forcing 120 flights to be cancelled, according to local reports. By 7pm that day, the visibility had dropped from 800 to 175 metres. Incoming flights already off the ground were diverted to other airports. Several flights from Hong Kong were forced to return to the SAR halfway into their journey. Yesterday afternoon air traffic resumed, but mayhem continued. Passengers turned away from the airport on Monday night returned to queue for new tickets and others came to meet travellers who had finally arrived after delayed flights. Ticket counters, security check queues and information desks were besieged and the lobby was crowded with travellers and their luggage. Nowhere inside the airport did signs mention that fog had caused the problems. 'It's really annoying, a complete mess,' said Liu Dong, who was waiting for an American colleague who was due to arrive from Osaka - his second wait in as many days. He blamed airport management for not providing more waiting space, more precise flight updates and more courteous information staff. Meanwhile, more than 1,000 passengers were held up at Chek Lap Kok as the fog forced the delay of nine China-bound flights and the cancellation of three more. Air China's check-in counters were deluged with irritated passengers and an argument broke out between an airline official and about a dozen Hong Kong passengers. 'We're burning with anger,' one indignant woman traveller said. The Beijing Weather Observatory said the fog was expected to ease today.