China’s most advanced stealth fighter jet, the J-20 , has a new engine that has significantly boosted its performance, according to a military source. The WS-15 afterburning turbofan engine was developed in China and has increased manoeuvrability and combat capability, said the source, who requested anonymity because of the sensitivity of the matter. That could take the J-20, or Mighty Dragon, a step closer to rivalling the American F-22 Raptor. The engine upgrade was highlighted on Chinese state television on Sunday, with CCTV saying the WS-15 had been put through a series of tests. The report did not say when the engine would be ready for assembly, but according to the military source that process has already begun. “The J-20s are fitted with the Russian AL-31F engines and these will be gradually be replaced by the WS-15,” the source said. They said there would be no change to the J-20s which have another Chinese engine, the WS-10C, also a thrust-vectoring engine. “In the future, all J-20s will be fitted with Chinese engines,” the source said. “This is part of the localisation programme [by the People’s Liberation Army ].” Andrei Chang, editor-in-chief of the Canada-based Kanwa Asian Defence Monthly , said that while the WS-15 engine upgrade could take it closer to competing with the F-22 – as well as America’s F-35 multirole strike fighter and Russia’s Su-57 stealth fighter – the F-22 would “remain a threat to the PLA”. “The aircraft is still the world’s most powerful fighter jet,” Chang said. “Besides its powerful engine, the F-20 is equipped with so many advanced technologies that still remain mysterious to outsiders.” Opinion: How emerging technologies are driving China’s readiness for modern war China’s military at present operates a fleet of about 50 J-20s. The military source said any new J-20s would be equipped with the WS-15 engine. In comparison, the US military has more than 180 active F-22s, but Washington decided in 2011 to stop production due to their high cost and expensive maintenance, so the F-35 is now the main challenge to China’s J-20. The F-22s have F-119 engines with afterburners and two-dimensional thrust-vectoring nozzles, while the F-35s use General Electric’s XA100 engine. Zhou Chenming, a researcher from the Yuan Wang military science and technology think tank in Beijing, said the American XA100 engine was still about a decade ahead of the WS-15 in terms of the technology. “China has so far just matched the American engines in some areas, but not in overall performance. It’s also not meaningful to emphasise one area because military confrontation is about a competition of systems and a contest of joint operational capabilities,” Zhou said. “The Americans still rule the sky in the Asia-Pacific because it’s not China’s intention to challenge US air superiority [in the region],” he added. China began developing the WS-15 engine in the early 1990s for fifth-generation aircraft like the J-20 but the project fell behind schedule, according to the CCTV report. The delay meant the developer of the J-20 – Chengdu Aircraft Industry Group – instead used the Russian AL-31F engine, as well as Chinese engines the WS-10B and WS-10C, amid increasing security challenges from the US. The Pentagon started deploying F-35s to the Asia-Pacific in recent years, pushing Beijing to speed up development of the J-20, which was first commissioned in 2017, six years after its maiden flight.