* 2 stealth fighters open show with brief flypast
* 'Big step forward in China combat capability' - expert
* Too early to say if J-20 matches U.S. F-22 jet - analysts
ZHUHAI, China - China showed its Chengdu J-20 stealth fighter in public for the first time on Tuesday, opening the country's biggest meeting of aircraft makers and buyers with a show of its military clout.
Airshow China, in the southern city of Zhuhai, offers Beijing an opportunity to demonstrate its ambitions in civil aerospace and to underline its defence ambitions. China is set to overtake the U.S. as the world's top aviation market in the next decade.
Two J-20 jets, Zhuhai's headline act, swept over dignitaries and hundreds of spectators and industry executives gathered at the show's opening ceremony in a 60-second flypast, generating a deafening roar that was met with gasps and applause and set off car alarms in a parking lot at the site.
"It is clearly a big step forward in Chinese combat capability," said Bradley Perrett of Aviation Week, a veteran China watcher.
Analysts say it is too early to say to what extent the new Chinese fighter can match the radar-evading properties of the Lockheed Martin F-22 Raptor air-to-air combat jet, developed for the U.S. Air Force and the J-20's closest lookalike, or the latest strike jet in the U.S. arsenal, Lockheed's F-35.
Unofficial shots of a J-20 prototype fuelled discussion over the region's power balance when first glimpsed by planespotters in 2010. Experts say China has been refining designs in hopes of narrowing a military gap with Washington.
Cao Qingfeng, an aircraft engineer watching the flypast, said the "stunning" display was a show of China's strengthening aircraft industry and manufacturing - and Western officials agreed.
"This shows they now have confidence to put it out in public," said a Western industry official who has monitored the biennial show from its inception 20 years ago.
"This is the airplane for China in the way that the J-31 is not; this is the one they develop for themselves," he added.
The export-oriented J-31, was unveiled at Zhuhai in 2014.
AIRBUS, BOEING RIVAL
President Xi Jinping has pushed to toughen the armed forces as China takes a more assertive stance in the region, particularly in the South China and East China seas.
It remained unclear whether or how the J-20 would be displayed after the flypast, or to what extent foreign executives and media would be allowed a close look as they try to figure out its role and effectiveness. Some foreign observers have questioned its stealth capabilities.
Aircraft that are already scheduled to be on display alongside the latest Chinese weapon systems, radar and drones include the Xian Y-20 strategic airlifter, and what organisers say is the largest amphibious plane now in production, the AG600.
The flying boat is officially promoted as a fire-fighting or search and rescue plane. But analysts note the AG600 - first unveiled 10 days after a Hague tribunal ruled against China's claim to parts of the South China Sea in July - is well suited to resupplying military outposts in the disputed area.
Notably absent from the airshow schedule is the Comac C919 passenger jet, designed to compete with Europe's Airbus Group and Boeing Co of the United States, the rivals who dominate the global supply of airliners.
The 150-seater C919 is scheduled to stage an often-delayed maiden flight this year, but industry sources say this will now slip to 2017 - three years behind original plans.
Airbus and Boeing continue to expand in China with recent plant announcements. Boeing is expected to announce a new supplier partnership at the show, which runs until Nov 6.