A Chinese test pilot refuted allegations that the country's new J-20 stealth fighter aircraft used copied parts from a Lockheed F-117 Nighthawk downed in 1999.

Controversy, as well as excitement, has swirled around China's J-20 since it was unofficially revealed to the public earlier this month in Chengdu, Sichuan Province. Several videos of the test flight appeared on Internet sites.

Chinese President Hu Jintao told U.S. Defense Secretary Robert Gates about the flight of the prototype J-20 shortly before Gates left Beijing after a three-day visit to China intended to improve military communications between the two countries.

Few details are available about the J-20, a joint design and development project by the Chengdu Aircraft and Shenyang Aircraft companies.

However, it has been compared in the aviation and security industry media to the Lockheed Martin's F-117 Nighthawk, a stealth ground attack aircraft operated by only the U.S. Air Force between 1983 and when it was officially retired in April 2008.

Since the J-20's test flight was acknowledged, a Croatian admiral who served during the Kosovo War in 1999 has come forward questioning where China gained some of the technology.

Adm. Davor Domazet-Loso said Chinese agents scoured the area in Serbia where the Serb army shot down an F-117 during a bombing raid on Belgrade. The agents' goal was to find parts of the plane in the countryside and also to pay local people for parts they may have picked up,' the admiral said.

"At the time, our intelligence reports told of Chinese agents crisscrossing the region where the F-117 disintegrated, buying up parts of the plane from local farmers," he said. "We believe the Chinese used those materials to gain an insight into secret stealth technologies."

But in a report on the Chinese news Web site Global Times, one of China's top test pilots denied the J-20 has any parts copied from what he called the obsolete F-117.

"Different from previous fighters such as the J-7 and J-8, which drew on the merits of aircraft from other countries, the J-20 is a masterpiece of China's technological innovation," Xu Yongling said.

It would have been impossible for China to glean technology from the F-117, he said. The F-117's stealth technology lags far behind fourth-generation fighters and was regarded as "outdated" even at the time when it was reportedly shot down.

Xu also said it would be hard to copy the radiation-absorbent, exterior coating technology used by the F-117 because not much likely survived the crash.

Instead, he said the J-20 is more like the U.S. Air Force's Lockheed Martin's F-22 Raptor stealth jet and Russia's first stealth fighter, the Sukhoi T-50, which had its first test flight in January 2010 and is expected in service sometime after 2015.

Immense secrecy surrounds the development of stealth fighters. The F-117 is a product of the Skunk Works and a development of the Have Blue technology demonstrator. The aircraft is about the size of an F-15 Eagle and its black color and sharp-angled wedge shape is to deflect radar signals.

The single-seat Nighthawk is powered by two non-afterburning General Electric F404 turbofan engines. Maximum speed was around 617 mph with a range of 930 nautical miles and a ceiling height of 45,000 feet.

The aircraft's first flight was in 1981 and it became operational in October 1983 but it wasn't officially acknowledged and revealed to the world until November 1988.

Wang Yanan, an associate editor in chief of Aerospace Knowledge magazine in Beijing, disputed any similarity between the J-20 and the F-117.

"Despite being dubbed a stealth fighter, the F-117 functioned as a bomber because of its low speed and limited air attacking abilities, while the J-20, more resembling the F-22, is designed to have a powerful air-attack capability with a fast flying speed," Wang said.

The single-seat F-22, made by Lockheed and also Boeing Integrated Defense Systems, entered service in 2005. Maximum speed is 1,500 mph with a range of 1,840 miles and a ceiling height of 65,000 feet. Power is from two Pratt & Whitney F119-PW-100 Pitch Thrust vectoring turbofans.

U.S. technological advances may provide reference points for many countries, Wang said. But secrecy surrounding such developments means countries like China must come up with their own technological answers.

An unnamed official at China's Ministry of National Defense told Global Times that "it's not the first time foreign media has smeared newly unveiled Chinese military technologies. It's meaningless to respond to such speculations."