Air China Ltd., Beijing's biggest carrier, and China Eastern Airlines Corp. fell to their lowest in about 17 months in Shanghai trading on concerns that this month's Olympics will damp passenger traffic.

Air China, also the country's largest international carrier, closed 8.2 percent lower at 7.18 yuan. China Eastern, the nation's third-largest carrier, fell 6.2 percent to 5.79 yuan. China Southern Airlines Co., the country's biggest carrier, dropped 3.1 percent to 5.90 yuan.

China has tightened visa regulations and curbed regular Beijing flights to boost security and ease congestion during the games. The big three carriers have all plunged at least 70 percent this year on concerns that rising fuel prices, weakening demand and a slowdown in the yuan's gains will crimp profit.

"The airlines' traffic figures have been reduced significantly by the Olympic Games,'' said Li Jun, an analyst at Everbright Securities Co. in Shenzhen. "The government has asked companies to restrict business travel to guarantee safety.''

The three airlines will release their July traffic figures as early as today. The country's airlines carried 14.2 million passengers in June, 3.8 percent less than a year earlier, according to the Civil Aviation Administration of China.

The country's carriers may also suffer from the yuan's decline against the dollar, as this will boost the value of their overseas debt. China Southern made a currency gain of 2.83 billion yuan ($296 million) in 2007 as the yuan strengthened. The gain was more than its 1.87 billion yuan net income. Air China made a 2.03 billion yuan gain.

The Chinese currency has dropped 0.7 percent since China's Politburo, the Communist Party's top decision-making body, said on July 25 that maintaining economic growth is as important as controlling inflation.

In Hong Kong, China Southern fell 6.7 percent to HK$2.51, China Eastern dropped 9.1 percent to HK$1.79 and Air China closed 0.5 percent lower at HK$3.69.