China has reportedly crossed another critical threshold in military aviation, flying an upgraded version of its J-20 stealth fighter equipped with the long-awaited high-thrust WS-15 engines and improved avionics. The development places Beijing in an elite club of nations capable of designing and producing advanced powerplants for modern combat aircraft and significantly enhances the operational potential of its premier fifth-generation fighter.
Already the second country after the United States to field two types of fifth-generation fighter jets and flight-test two sixth-generation fighter programs, China’s latest progress underscores the rapid maturation of its aerospace and propulsion industries. State-run media recently released new footage showing flight tests of an upgraded J-20A stealth fighter, widely believed to be powered by the WS-15 engines that Chinese engineers have pursued for more than a decade.
The footage was released by the Aviation Industry Corporation of China (AVIC), the state-owned aerospace giant and manufacturer of the J-20. According to a social media post by state news agency Xinhua, the aircraft shown are new prototypes of the J-20A, an upgraded variant of the original J-20 stealth fighter that entered service with the People’s Liberation Army Air Force (PLAAF) in 2017.
Significantly, the video shows at least three J-20As painted in a yellow zinc-chromate primer. In China’s aerospace industry, this coating typically indicates an aircraft in the late stages of testing, applied to protect the airframe before the final stealth coatings are added ahead of delivery to frontline units. Analysts say this suggests flight testing of the WS-15-powered variant is nearing completion and that the aircraft may be entering a pre-delivery evaluation phase.
With the apparent operationalization of the WS-15, China has joined a small group of countries capable of producing advanced engines for modern combat jets. Until now, only five nations have demonstrated this capability: the United States, through companies such as General Electric and Pratt & Whitney; the United Kingdom with Rolls-Royce; France via Safran; Russia through manufacturers including NPO Saturn and Klimov; and China, represented by the Aero Engine Corporation of China (AECC).
What sets the WS-15 apart, analysts say, is that it finally places China in the top tier of high-thrust fighter engine producers. The WS-15 is often compared to the Pratt & Whitney F135 engine that powers the F-35 Lightning II, widely regarded as the most powerful fighter engine currently in service.
These high-thrust engines are a defining feature of fifth-generation fighters. They enable sustained supersonic cruise—commonly known as “supercruise”—without the use of afterburners, dramatically improving fuel efficiency, range, and survivability while reducing infrared and radar signatures.
This is not the first time that J-20 aircraft equipped with WS-15 engines have been observed. In September last year, J-20As were spotted during flight tests with the new engine, and by December, reports suggested that the upgraded variant had entered serial production. However, the latest official footage appears to confirm that the aircraft has progressed beyond experimental trials and is edging closer to frontline deployment.
The WS-15 is expected to transform the J-20A’s performance envelope. Apart from powering advanced avionics and electronic warfare systems, the engine provides a substantial boost in thrust, enabling sustained supersonic cruise and improving overall agility and payload capacity.
Abraham Abrams, a leading expert on China’s stealth fighter program, highlighted the engine’s significance in his book J-20 Mighty Dragon. He noted that the WS-15 boasts a “much higher thrust-to-weight ratio estimated at 10:1 or 11:1, requires less maintenance, improves thermal management properties, and has a significantly longer service life.”
“Its cutting-edge single-crystal turbine blades, although proving particularly difficult to mass produce, were expected to almost double the engine’s lifespan compared to the WS-10B while significantly lowering maintenance needs,” Abrams wrote.
According to China’s state broadcaster CCTV, the WS-15 can generate up to 18.5 tonnes of thrust—comparable to the F135 engine used on the American F-35. This level of thrust allows the J-20A to sustain supersonic flight without engaging afterburners, a capability long considered a hallmark of true fifth-generation fighters.
Reports suggest that a WS-15-equipped J-20A can cruise at speeds around Mach 1.8, with a theoretical maximum speed estimated between Mach 2.5 and Mach 2.8, though such figures remain unverified.
The J-20’s evolution has been closely tied to China’s struggle—and eventual success—in mastering advanced jet engine technology. In its eight-year operational lifespan, the aircraft has flown with three different types of engines.
When the J-20 first entered service in 2017, it relied on the Russian-made Saturn AL-31F afterburning turbofan. While proven and reliable, the AL-31F did not generate sufficient thrust for sustained supercruise, limiting the J-20’s ability to fully meet fifth-generation performance benchmarks.
The AL-31 family of engines has powered a wide range of Russian and Chinese fighter aircraft, including the Su-27, Su-30, Su-34, J-10, and J-11. Variants such as the AL-31FP incorporate thrust vectoring, while others have been adapted for different airframe requirements. Despite their versatility, these engines represented a technological ceiling for China’s early stealth ambitions.
In 2019, the J-20 transitioned to the domestically produced WS-10C engine. While a major step forward, the WS-10C is believed to allow only limited supersonic cruise, falling short of the full performance expected from a fifth-generation platform.
The first confirmed sightings of J-20 aircraft fitted with the WS-15 emerged in 2024, marking what many observers described as a watershed moment for China’s aerospace industry.
China’s progress is particularly striking given its historical reliance on foreign engines. Despite developing a range of indigenous fighter aircraft over the past several decades, Beijing depended heavily on Russian propulsion technology well into the 2000s.
This began to change with the introduction of the WS-10 engine, which achieved design certification in 2005. At the time, it represented China’s first credible attempt at a modern combat jet engine. Two decades later, the apparent maturation of the WS-15 suggests China has closed much of the gap with the world’s leading aerospace powers.
From producing its first certified combat jet engine to developing a true fifth-generation powerplant in just 20 years is widely seen as a remarkable technological leap.
Fu Qianshao, a retired PLAAF colonel, told the Hong Kong-based South China Morning Post that if the engine shown in the footage is indeed the WS-15, the increase in thrust would be substantial.
“Although fuel consumption will increase, it will be very beneficial for the J-20A to achieve supersonic cruise,” Fu said.
The upgraded J-20A is not defined by its engines alone. Observers have noted visible changes to the airframe, most notably a substantially raised dorsal spine behind the cockpit—often dubbed the “fat-neck” J-20.
Fu said this modification was likely intended to create additional space for upgraded avionics, sensors, and electronic warfare systems, though it could also marginally increase aerodynamic drag.
“If the airframe design modifications are done well, the changes in air resistance won’t be too significant,” he said. “And if the new engines are replaced, this drag won’t have a major impact.”
He added that the expanded dorsal section may also allow the aircraft to carry additional fuel, further extending its range.
According to a recent research paper by the UK-based think tank Royal United Services Institute (RUSI), China could deploy as many as 1,000 J-20 heavy stealth fighters by 2030. A significant portion of these could be upgraded J-20A variants powered by the WS-15 engine.
Beyond the J-20, analysts believe derivatives of the WS-15—or technologies developed for it—could be adapted for China’s under-development sixth-generation fighter programs, potentially shaping the next phase of aerial combat.
The operational deployment of the WS-15-powered J-20A would mark a decisive moment for China’s military aviation, signaling not only the arrival of a more capable stealth fighter but also Beijing’s emergence as a top-tier jet engine power—a feat long considered one of the most difficult in modern aerospace engineering.
