http://news.jstv.com/a/20160108/1452234702366.shtml
back in 2016, China offered the copy right of L-15 to Ukraine. Ukraine was interested at first, because original L-15 uses Ukraine engine, so it is cheap for Ukraine and a very good deal for Ukraine logistically. But US pressurised them not to purchase any, and made them purchased A-29 instead, which is a far inferior plane.
Because of that, Ukraine still had no ability to produce advanced fighter on their own and have to make do with old Soviet era planes like Su-27SK and MiG-29S. All of those can be easily out matched by Russian planes like Su-30 and Su-35. And that is why Russian took control of Ukraine air space in the matter of days. I bet Ukraine is really regretting their decide right now. If they had taken the deal, Russian planes would have to deal with PL-12 today instead of R-27.