SYDNEY/SINGAPORE (BLOOMBERG) - Killing four empty hours at Guangzhou airport waiting for a China Southern connection to Sydney may not be everyone's idea of fun. For Gina Capella, it was a no-brainer.

The 43-year-old Boston resident and her friend saved hundreds of dollars last year choosing China Southern Airlines over a direct flight from Seoul with Korean Air Lines or Asiana Airlines.

"We didn't mind the layover because it was so much cheaper," she said. "Like, almost half the price."

Chinese airlines are flooding the world with some of the lowest long-haul fares ever seen - and delivering a hammer blow to foreign carriers trying to keep up. From Delta Air Lines and American Airlines Group in the US, to Cathay Pacific Airways and Korean Air, many operators are feeling the squeeze from the extended reach of mainland Chinese carriers.

They don't just offer cheap fares on routes long-dominated by national airlines like Korean Air. They're also adding hundreds of overseas flights from little-known Chinese cities to airports all over the world.

"Chinese airlines are still hardly scratching the surface of their potential, not just in China, but globally," said Will Horton, a Hong Kong-based analyst at the CAPA Centre for Aviation. "If an airline today cannot compete with or grow alongside a Chinese airline, the future will be bleak."

According to CAPA, mainland Chinese airlines have opened 75 long-haul markets since 2006, led by Air China and Hainan Airlines. More than two-thirds of those routes opened only in the past two years. China's three biggest carriers - Air China, China Eastern Airlines Corp. and China Southern - are state-controlled and listed in Hong Kong and Shanghai.

Cathay, where first-half profit sank 82 per cent as Chinese travelers bypassed its Hong Kong base, is now conducting what it calls a "critical review" of its business.

Delta President Glen Hauenstein told analysts in October that China "continues to be challenged" as capacity growth outpaces demand. American Airlines President Robert D Isom said the same month there's "continued weakness in China" as excess capacity seeps into the airline's new services from Los Angeles to Hong Kong, Haneda, Sydney and Auckland.

A round trip with China Eastern between New York and Bangkok, via Shanghai, costs US$570.06, according to Webjet.com. The same trip with United Airlines through Hong Kong costs US$714.80. Flying from Los Angeles to Hong Kong with China Airlines is one third cheaper than with American Airlines.

"US airlines dominated the China-US route in the past, but now it's the Chinese airlines," said Chen Suming, an analyst at Shanghai Chongyang Investment Management Co. "Most of the new air travelers are from China, not the US."

China Southern is selling flights from Sydney to Seoul, via Guangzhou, for US$588.30. That's more than one third cheaper than flying direct with Qantas Airways. Getting from London to Hanoi in Vietnam, also via Guangzhou, costs just US$830 with China Southern. British Airways charges US$1,216.50.

Price isn't everything. Cathay and Singapore Airlines both have a five-star rating for product and service from airline rating system Skytrax. Hainan Airlines is the only mainland Chinese carrier among the world's nine top-rated airlines. National carrier Air China has three stars.

There's little sign the inundation will end. International air routes in China jumped 35 per cent to 660 last year, the Civil Aviation Administration of China said. By 2021, Chinese will be the top overseas visitors to the US, according to the U.S. government.

For years, the easiest way to get to a second- or third-tier city on the Chinese mainland was to fly to long-established transit centers such as Hong Kong, Shanghai or Beijing and then take a local connection. Now a new world order is emerging. Chinese carriers in these cities are sidestepping hubs such as Singapore and Hong Kong and flying straight to destinations abroad. That poses the biggest threat to airlines such as Cathay and SIA.

This month, Hainan started flying non-stop to Las Vegas from Beijing, its 10th route to North America. Hainan also operates at least eight flights to European cities. Meanwhile, British Airways is halting its London-Chengdu service in January because it's not viable.

Demographics partly explains the proliferation of flights from China and the lop-sided, mainly-Chinese flow of passengers. Chengdu has a population of more than 14 million. Even the population of Xiamen, on China's southeast coast across from Taiwan, is nearing Sydney's 4.3 million.

"While it might not work for foreign carriers to fly to second-tier cities like Chengdu and Xiamen, it will still work for the Chinese because the originating market is very big," said K. Ajith, an analyst at UOB Kay Hian Pte in Singapore. "There's an underlying desire to travel."

That's borne out in forecasts for new aircraft. Chinese airlines will need 6,810 new planes valued at US$1 trillion in the next two decades to meet travel demand, according to Boeing Co.

Meanwhile, US airlines are seeking to bolster ties with Chinese carriers. Delta invested US$450 million in China Eastern in July 2015 for a 3.6 per cent stake. United Continental Holdings this year signed a deal with Air China to improve connections and enhance frequent flier benefits between the airlines.

To be sure, rising jet fuel prices, spurred by Opec's production cuts in November, may hold back some of China's expansion, said Ajith, the analyst at UOB Kay Hian. While capacity growth on routes between the US and Shanghai, Beijing or Guangzhou has been "off the charts," Chinese airlines have "maxed out" under the current bilateral agreement, said Kris Kelley, an airline analyst at Janus Capital Management.

All the same, Australia's government announced on Dec 4 an agreement with China to remove all capacity restrictions between the two nations. In October, Britain agreed to double the number of flights between UK cities and China.

Chinese airlines are improving their business class, too, giving them confidence to compete around the world, according to Horton, the analyst at CAPA. With every new generation of aircraft, that level of service only improves, he said.