China has decided not to buy the high-performance JL-15 jet trainer it has been developing (with help from Russian and Ukrainian firms) for nearly a decade. At least not yet. The 9.5 ton, twin engine JL-15 can achieve supersonic speeds, and has the kind of high-tech cockpit found in modern fighters. The JL-15 was designed to be produced in two versions; advanced trainer, and initial fighter trainer. This would smooth the transition to high end aircraft like the J-10 (similar to the F-16) and J-11 (an Su-27 clone).
Instead of the JL-15, the air force and navy are buying JL-9s. This is an upgraded version of the JJ-7 trainer, which was based on the J-7 (a Chinese copy of the Russian MiG-21). The JL-9 has side air intakes, and a radar dome up front. It doesn't look a lot like a MiG-21, and is somewhat easier to fly. While the JL-15 is a few years away from production, the JL-9 just entered production and is several million dollars cheaper than the twin-engine JL-15. Apparently, the Chinese believe that it's better, and cheaper, for new J-10 and J-11 pilots to learn in these aircraft, rather than spending more time in the pricey, but similar in performance, JL-15s.