By JEREMY PAGE
BEIJING—Chinese military experts disputed that China obtained secret U.S. technology to develop its new stealth fighter, saying the country relied on homegrown innovation to produce a plane that has drawn new international attention to its military advances.
Speculation that China obtained U.S. stealth technology has been circulating since aviation experts noted that the J-20 stealth-fighter prototype looked like a larger version of the U.S. F-22 Raptor, currently the world’s only fully operational stealth fighter. The twin-engine J-20 made its first public test flight two weeks ago during a visit to China by U.S. Defense Secretary Robert Gates.
On Sunday, the Associated Press quoted Balkan military officials saying China likely learned some of its stealth technology from pieces its agents obtained of the wreckage of a U.S. F-117 shot down by a Serbian anti-aircraft missile during the 1999 Kosovo war. The F-117 Nighthawk was the first U.S. stealth fighter.
Then, on Monday, a former U.S. B-2 stealth bomber engineer called Noshir Gowadia was sentenced by a U.S. court in Hawaii to 32 years in prison for selling stealth-missile technology—with potential applications on fighter jets—to China.
Mr. Gowadia’s son, Ashton Gowadia, said his father plans to appeal.
“China is completely capable of making its own stealth fighter jet,” said Li Daguang, a professor at the People’s Liberation Army’s National Defense University. “I think we developed the J-20 largely on our own research, but at the same time learning from existing foreign models. Many countries have already possessed stealth-jet technology…stealth materials are not considered highly sophisticated or confidential at all.”
China’s Defense Ministry and Air Force declined to comment on any of the reports, as did China Aviation Industry Corp., which is developing the J-20, and the Chengdu Aircraft and Design Institute, where it is being tested. Asked about the reports at a routine briefing, Foreign Ministry spokesman Hong Lei said “I am not aware of relevant information.”
Song Xiaojun, a former naval officer who is now a military commentator for Chinese state television, attributed the reports that China appropriated its stealth technology to those who “just envy and hate us for having developed the jet, for we made something they thought we’d never be able to make. I’m saying that I’m sure the technology is 100% Chinese.”
The Wall Street JournalOn display at Air Show China in Zuhai late last year: this CIA-style drone with missiles.
The AP quoted Adm. Davor Domazet-Loso, Croatia’s military chief of staff during the Kosovo war, as saying intelligence reports in 1999 described Chinese agents “criss-crossing” the region where the F-117 went down, and buying bits of wreckage from local farmers.
“We believe the Chinese used those materials to gain an insight into secret stealth technologies … and to reverse-engineer them,” he was quoted as saying.
Parts of the F-117 are still exhibited at Belgrade’s aviation museum.
Still, other analysts point to signs of Chinese interest in the F-117. Andrei Chang, the Hong Kong-based editor of Kanwa Defense, an online publication about military affairs, said China had also built a scale model of the F-117 at an aviation research institute in the city of Luoyang in Henan province.
He included in an emailed statement what he said was a satellite photograph of the F-117 model, taken in May 2010.
“This is the fundamental reason why it took China only a very short period of time to develop several types of stealth materials in Beijing,” he said.
The B-2, which was developed in the 1980s and first unveiled in 1988, is still used as a long-range strategic bomber and has never been shot down.
Mr. Gowadia—the former B-2 engineer sentenced Monday—moved from India to the U.S. for postgraduate work in the 1960s and became a U.S. citizen about a decade later.
He helped design the propulsion system for the B-2 when he worked at Northrop Corp., now known as Northrop Grumman Corp., between 1968 and 1986.
He was arrested in 2005. A federal jury in Honolulu found that he pocketed about $110,000 to help China design a cruise-missile exhaust nozzle that would give off less heat, allowing it to evade infrared radar detection and U.S. heat-seeking missiles.
He was not accused of assisting with the J-20 program, although prosecutors did say that he visited an aviation design facility in Chengdu, the western city where the stealth fighter has been tested.
However, aviation experts have noted that the J-20 prototype that made the test flight had unusual exhaust nozzles, which appear to be designed to prevent it from emitting enough heat to be detected by infrared radar.
—Yoli Zhang and Juliet Ye contributed to this article.