CHINA Southern Airlines Co, Air China Ltd and China Eastern Airlines Corp, the nation's big three carriers, all surged by the daily limit in Shanghai trading as falling jet-fuel prices spurred optimism about airlines' profit.

China Southern, the biggest Chinese carrier, climbed by the 10 percent maximum to 13.92 yuan at the close of trading. Air China jumped to 16.31 yuan and China Eastern leapt to 11.79 yuan, Bloomberg News reported.

The airlines rose after the price of jet fuel, the biggest cost for most Asian carriers, declined for a third straight day on Friday. The carriers' Shanghai stocks were also catching up with gains made by Hong Kong shares on Friday when mainland stock markets were closed for a national holiday.

"Fuel costs will decrease," said Kenny Tang, a research director at Tung Tai Securities Co in Hong Kong. "The major problem for airline stocks over the past one to two years has been the high oil prices."

Jet fuel prices fell 2.6 percent to US$137.85 a barrel in Singapore on Friday.

The price has declined 5 percent since hitting a record close of US$145.05 on April 28. It has climbed 70 percent over the past year.

Chinese carriers have also benefited from the yuan's 4.3 percent appreciation this year, because this cut the value of their debt denominated in dollars.

"If you take out the foreign-exchange gains, a lot of airline companies would have made losses due to high oil prices," Tang said.

Shanghai Airlines Co, China's fifth biggest carrier, also rose by the 10 percent limit to 9.44 yuan. Fourth-ranked Hainan Airlines Co climbed 9 percent to 9.17 yuan.

China Southern's Hong Kong stock rose 2.9 percent to HK$5.70 at the 4pm close, after gaining 9.1 percent on May 2.