An unverified photo apparently showing the FC-31 prototype on a test flight

Photo circulating online suggests it has undergone modifications including to the canopy over its cockpit and wind resistance improvements. But it appears to have retained engine based on a 1970s Soviet design that is seen as a limitation to its function and capabilities

A Chinese aviation company has apparently been test flying its new stealth fighter jet that aims to match America’s F-35s, and which could be a candidate for its next generation of ship-borne warplanes.

The latest prototype of the fifth-generation FC-31 Gyrfalcon may have undergone a number of modifications, according to a witness photograph circulating on social media network Weibo that appears to show the aircraft on a recent flight but could not be verified.

The stealth fighter is pictured using its fuel-guzzling afterburners as it gains altitude, with the logo of state-owned developer the Aviation Industry Corporation of China (AVIC) clearly visible on the jet’s tail.

Different from earlier versions, it appears the latest prototype no longer has an airspeed measurement device located in the nose of the jet, suggesting it could have been replaced with fitted avionics such as an active electronically scanned array, or AESA, radar.

The transparent canopy over the cockpit also appears to have changed to a design more like the one used in China’s other stealth fighter, the J-20.

There may have also been modifications to improve the jet’s wind resistance, according to the photo.

The Chinese stealth fighter has broadly similar specifications to F-35 Lightning-II

But the aircraft appears to have retained the WS-13 twin turbofan engines of previous FC-31s. The engine is based on a 1970s Soviet design and is seen as a limitation in terms of the fighter jet’s function and stealth capabilities.

The FC-31 is China’s second domestically developed stealth fighter jet after the J-20. It made its maiden flight in 2012 and has appeared at a number of air shows in the hope of attracting foreign buyers – AVIC had hoped it could compete with the American Lockheed Martin F-35 – but has failed to attract any. The Chinese air force has also declined to place any orders, even though it was primarily designed for use by the service.

But recent progress on the FC-31 suggests its developer has shifted focus to a naval version of the stealth fighter, according to military analysts, especially after an AVIC research and development unit said it aimed to start testing a new jet next year.

Being lighter and smaller than the J-20, the FC-31 could be a better fit for the PLA Navy’s next-generation aircraft carrier, which is expected to have a catapult launch system and will need a more advanced stealth fighter than the J-15 – its only carrier-based fighter in service.

The FC-31 has broadly similar specifications to the F-35 Lightning II. It has a maximum take-off weight of 25 tons, a combat range of 1,200km (746 miles) and a top speed of Mach 1.8, or 2,205km/h (1,370mph). By comparison, the F-35 has a maximum take-off weight of 27 to 32 tons, a range of up to 2,200km (1,367 miles), and a top speed of Mach 1.6. The Chinese FC-31 has a weapons payload of 8 tons, compared with 6.8 to 8.1 tonnes for the American F-35s.