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.
Gates, who is also visiting Japan and South Korea while in the region, said the discussion with Hu about the J-20 flight that took place this week was short.
"I asked President Hu about it directly and he said that the test had absolutely nothing to do with my visit and had been a pre-planned test. And that's where we left it."
The 15-minute flight took place in Chengdu, in southwest China.
Hu, who is chairman of the Central Military Commission, said the flight hadn't been timed to coincide with Gates's visit.
The 11-member commission issues directives to the army including senior appointments, troop deployment and arms spending. The majority of members are senior generals but several senior Communist party members are on the commission, a move said to ensure that the military remains loyal in its actions toward the government.
Defense and aviation analysts have been questioning images and video clips of the stealth fighter seen on Chinese Web sites since last month, showing what looks like a J-20 standing on a runway apron and then taking off.
Many of the shots of the Chengdu J-20 appear taken by people standing a long way from the runway, possibly outside the airport perimeter.
The aircraft was officially announced in late 2002 as being under development through a joint design and development project by the Chengdu Aircraft and Shenyang Aircraft companies.
But Chinese political leaders and aviation sector professionals have been guarded about details, specifications and development progress of the aircraft that is similar in concept to Lockheed Martin's F-22 Raptor stealth fighter.
However, experts have gleaned much information over the years.
The latest shots show an elongated airframe with forward canards, a main delta wing, outward canted fins, two small ventral fins, two under-wing diverterless supersonic intakes and conventional jet nozzles.
It is believed to be larger than the F-22 -- the only truly stealth plane operational -- or Russia's prototype stealth fighter, the Sukhoi T-50, which had its first test flight in January 2010 and is expected in service sometime after 2015.
It isn't clear what engine the J-20 is using. There was some speculation that the Russians may have supplied the 32,000-pound thrust 117-S engine because the Chinese-made WS-10A isn't ready.
The 117-S is an upgrade of the Saturn AL-31 turbofan engine developed by Lyulka, now NPO Saturn, of Russia. It was originally made for the Sukhoi Su-27 fighter.
It also remains open whether the plane uses plasma stealth technology whereby it emits an ionized gas that surrounds the aircraft, making it harder to detect by radar systems.