Strategy Page
On September 27th China announced that its J-20 stealth fighter had officially entered service. Earlier in 2017 Chinese officials admitted that at least a dozen J-20s had been delivered to the Chinese air force as part of a new fighter squadron. This information was apparently released to help with export sales because the recent official announcement comes at the same time that a recent Chinese press release about China-Pakistan relations seemed to confirm that Pakistan had agreed to buy J-20s. Numbers were not announced and there are still questions about how effective the J-20 actually is. Pakistani interest in the J-20 may have more to do with the fact that China is the only major-power ally they have, their main supplier of weapons and, best of all, a neighbor.
While China began offering its 18 ton J-31 stealth fighter to export customers in 2014 (as the FC-31), it was not until recently that efforts were made to export the more advanced J20. The manufacturer of the J20 (CAC. Chengdu Aircraft Company) also produces the JF-17 and J-10. The JF-17 is a joint effort with Pakistan and Pakistan is the main customer.
The J-20 made its first flight in 2011, and many more since then. Before mass production began in late 2015 eight prototypes were built. There were at least two original J-20 prototypes, and in 2013 a new prototype appeared that had several modifications and is estimated to have a max weight of 36 tons. Since then several more prototypes have been built along with at least twenty production models.
Work on the J-20 began in the late 1990s, and the Chinese knew that it could be 25 years or more before they had a competitive stealth fighter-bomber. The twin engine J-20 first appeared to be about the same weight class as the 30 ton F-15C but the production model was closer in weight to the F-22. The F-35A is a 31 ton, single engine fighter, while the twin-engine F-22 is slightly larger at 38 tons. The Russian T-50 weighed in at 37 tons.
https://www.strategypage.com/htmw/htairfo/articles/20171015.aspx
