In 1995, China secured the rights for domestic production of the Su-27SK by Shenyang under the designation J-11. As originally conceived, the J-11 was to be merely a Chinese-built Su-27SK - complete with Russian engines and systems. While the J-11 took flight in 1998 and quickly entered service alongside Russian-production Su-27s, Shenyang went to work on the development of an indigenous improvement to the design. Designated the J-11B, the new aircraft used domestically-designed WS-10 engines, domestically-designed onboard systems, and extensively employed composites to lower the empty weight by 700kg. The J-11B added the capability to mount a variety of Chinese-designed ordnance, including anti-ship missiles.
The J-11B has had its share of controversy. Its legitimacy has been called into question, as concerns have been raised over unlicensed production of the Su-27 design. Production has stopped of the original J-11s, apparently shifting to J-11B production, but, as is common with the Chinese, the domestically designed WS-10 engine has had many teething issues. Shenyang has looked to Russia for alternatives - the AL-31 series engines used on SU-30MKIs were a top choice for an alternative powerplant. At least one squadron did operate WS-10-powered J-11Bs briefly, but the aircraft were quickly grounded after the engines proved to have impractically short lives (30 hours compared to 400 for Russian engines). In spite of the issues, however, the J-11B has gone on to form the basis for further Chinese Flanker variants.