Airline shares surged on the Shanghai Stock Exchange on Monday, on anticipation that their US-dollar-denominated overseas debts would shrink considerably after the central bank signaled an end to the currency's peg to the dollar.

The People's Bank of China indicated during the weekend it was going to slacken a 23-month peg against the dollar, and let the yuan be more flexible.

Domestic carriers are tipped to be the biggest gainers from a stronger yuan, as all of them have run up huge international debts from buying Airbus SAS and Boeing Co planes.

Guangzhou-based China Southern Airlines Co Ltd currently has an overseas debt of 52.4 billion yuan ($7.71 billion), while the Beijing-based Air China Ltd owes 45 billion yuan and the Shanghai-based China Eastern Airlines has debt of 30 billion yuan, according to Li Lei, an analyst with Citic China Securities.

"The market expects the Chinese currency to rise between 2 and 3 percent in value. This will trim at least 1 billion yuan from each of the three carriers' US dollar debts," Li said.

Shares of China Southern Airlines Co Ltd, the nation's largest carrier by fleet size, rose 8.18 percent to close at 7.27 yuan on Monday, while Air China and China Eastern rose 6.44 percent and 5.59 percent respectively.

Although Air China operates the nation's largest amount of outbound flights, analysts considered China Southern as the biggest beneficiary due to its huge overseas debt.

The Guangzhou-based carrier just welcomed its 400th plane on Sunday, making it the world's sixth-largest carrier by fleet size. It is quickly expanding its aircraft numbers, and plans to add 12 new aircrafts this year.

Yao Jun, an industrial analyst with China Merchants Securities, said that each percentage point that the yuan rises would boost China Southern shares by 0.044 yuan, Air China by 0.025 yuan, and China Eastern by 0.021 yuan.

Yao said China Southern, Air China and China Eastern will write off their overseas debts by around 352 million yuan, 306 million yuan and 237 million yuan respectively, for every percentage point that the Chinese currency strengthens against the US dollar.

"A more expensive yuan is good news for international flights' fuel costs, as well as take-off and landing fees, and the biggest gains would be our overseas debts," said Rao Xinyu, board secretary of Air China.

According to Rao, the appreciation of the yuan will help reduce the Beijing-based carrier's capital expenditure, which is expected to reach 15 billion yuan this year. Nearly 70 percent of the capital expenditure is used to purchase aircraft and equipment.

The three leading carriers registered an encouraging first-quarter report earlier. China Southern posted a net profit of 1.419 billion yuan, five times higher than that of last year.

Air China posted a net profit of 2.17 billion yuan, up 121.33 percent over the same period last year, while China Eastern moved into the black after reporting a net profit of 770 million yuan.