The Chinese navy intensively exercised its upgraded J-11B fighter jets over the disputed South China Sea following mass delivery of the advanced model, according to state media reports. More than 10 fighter jets from the People’s Liberation Army’s Southern Theatre Command participated in “round-the-clock” training and battled in four-versus-two and two-versus-two formation, official broadcaster China Central Television (CCTV) reported. CCTV’s footage of the drill showed a J-11B returning from the exercise and entering its hangar, with the aircraft featuring a grey radar dome, unlike the black sported by the original versions. China’s J-20 stealth fighters are getting an engine upgrade, source says The change in colour has sparked speculation about its being a sign of a radar upgrade to a hi-tech active electronically scanned array ( AESA ) system, according to nationalist tabloid Global Times . The computer-controlled AESA system allows jets to communicate better, as well as detect targets earlier and at longer range. The J-11B is a significantly modified version of the Soviet-designed Sukhoi Su-27 fighter from state-owned Shenyang Aircraft Corporation (SAC). It remains the most advanced fighter jet operated by the PLA Navy’s land-based aviation force, alongside some Su-30MKK imported from Russia in the 2000s. The twin-engine multirole J-11B has a range of 1,500km, extendable with additional fuel tanks. It can also carry advanced weapons like the PL-10 short-range combat missile and the PL-15 beyond-visual-range air-to-air missile. This makes the jet an ideal instrument to defend Beijing’s vast claims to the South China Sea, which stretches 2,000km from its southernmost island of Hainan to cover almost the entire span of the waterway – in claims contested by five southeast Asian neighbours. The J-11Bs of the PLA Air Force were photographed as deployed on Woody Island, a Chinese-controlled military base in the disputed Paracel Islands in the South China Sea. In 2014, a J-11 fighter jet reportedly came within 10 metres of an American P-8A Poseidon submarine-hunter about 220km east of Hainan, with the PLA warplane flying past the P-8’s nose and performing a barrel roll at close range. China has militarised islands in South China Sea, says US admiral The J-11 series is based on the Sukhoi-27 following a 1998 agreement. And the J-11B is a significantly modified version with special home-made avionics, or electronics as applied to aviation. The SAC has delivered a massive number of J-11B, but mostly to the Chinese air force. It has further developed a more powerful J-16 for the force, based on the twin-seat J-11B. The SAC was first seen building a J-11B model for the PLA Navy as early as 2010. It also produces for the navy the J-15, a ship-based fighter for its aircraft carriers. The company has also been replacing the engines on the J-11Bs, both for the air force and navy, with the home-made WS-10 series – a thrust-vectoring engine that offers much higher manoeuvrability rivalled only by the US and Russia.