
A report posted online by China’s Xinhua News Agency suggests that the J-20 – China’s fifth-generation stealth fighter jet – has entered the mass production stage. The evidence is a photograph of a J-20 on the tarmac, coated with yellow primer paint and bearing the serial number “2101.”

Previous versions of the J-20 have been numbered in the 2000s (with the first prototype labeled 2001 and the most recent 2017). The appearance of a number in the 2100s hints to China’s online military enthuasists that production has entered the production stage – although Xinhua cautions that the initial production run for the J-20 may be limited at first. In particular, unnamed experts cautioned that the software used in fifth-generation fighters will need additional testing, even if the body of the aircraft is finalized.

Experts interviewed by Xinhua said the J-20 would have progressed to production quite quickly if the rumors are true. The first J-20 took flight in 2011, less than five years ago. Xinhua notes there were no major changes from the previous images of the 2017 version to this new 2101 J-20, meaning the design is already fairly set, with only minor alterations expected from here on out. Critics believe the design has progressed so quickly because China based its J-20 on stolen plans for the United States’ F-22 and F-35.

The J-20 is China’s first attempt at a stealth fighter, and details are scarce. Observers are not even certain which engine the planes will use, whether China’s indigenously-created WS-15 or a Russian import, such as the AL-31 used in earlier J-20 prototypes (China may also be interested in reverse-engineering the new AL-117S engine used in 24 Su-35s Beijing just purchased from Russia).

According to the U.S. Department of Defense’s 2015 report on military developments in China, the People’s Liberation Army Air Force is pursuing two separate stealth fighter programs (the J-20 and J-31) “to improve its regional power projection capabilities and strengthen its ability to strike regional airbases and facilities.” The J-20 is expected to have a top speed of Mach 2.5 and a combat range of around 2,000 kilometers (1,200 miles), according to GlobalSecurity.org.

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The stealth capability in particular is seen as crucial in China’s development of an air force capable of conducting offensive operations abroad, and Beijing takes it particularly seriously. According to a Chinese military expert cited by Xinhua, the J-20 is supposed to have stealth capabilities surpassing those of its Russian competitor, the T-50.

According to the Pentagon, China’s J-20s “could enter service as early as 2018.”