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The first photos and videos showing China's J-20 stealth fighter equipped with an air-to-air missile (AAM) appeared on the Internet Tuesday. The unique side-weapon bay design fully demonstrates Chinese engineers' creativity, experts say.

In pictures first uploaded to the military forum iissbbs.com, the 2002 prototype was seen making turns over Chengdu, Sichuan Province, with a new infra-red AAM, which is widely believed to be the PL-10, a next-generation missile comparable to its foreign counterparts such as the US AIM-9X.

Judging from the pictures, J-20's rotatable missile pylon allows its side weapon bay door to close after the pylon rotates out of the bay, unlike those found on US stealth jets, in which the weapon bay doors have to remain open after the missile pops out in order to get a target lock-on, Bai Wei, former vice editor-in-chief of the Aviation World Monthly, told the Global Times.

Stealth fighters carry AAMs in weapon bays in order to keep low radar visibility. Both the J-20 and the US F-22 have a big, central weapon bay to carry mid- and long-range missiles and two smaller side bays for accommodating short-range AAMs, which are often used in dogfights, which usually involve intense maneuvers. Operational conditions for weapon bays become harsher if a dogfight takes place at supersonic speed.

"The J-20's bay design is unique and very creative. It may help reduce drag and avoid engineering difficulties such as managing structural strength and aerolasticity," Bai said.

Its deployment device shows that Chinese engineers are not simply copying US technology. If not improving it, they are at least troubleshooting some of the issues already faced by their American counterparts with clever ideas, commented aviationist.com.

"The fact that the J-20 has begun weapon integration tests over two years after its maiden flight shows the project is going pretty smoothly," Bai added.

At least two J-20s have been produced. The country's second stealth fighter, dubbed by outsiders as the J-21, is also undergoing flight tests in Shenyang, Liaoning Province, local witnesses told the Global Times.