China recently ended production of its MiG-21 clone (the J7) after nearly fifty years of manufacturing what evolved into an advanced version of the original Russian design. China began licensed production of the Russian MiG-21 in 1964, but it took another decade for that to evolve into the J7 and for mass production to really get started. Over 2,400 were produced. The earlier ones were inferior to the MiG-21 because Russia refused to transfer technology for the latest models of this 1950s design. By the 1980s the Chinese had matched the Russian MiG-21. This didn’t bother the Russians because in 1985 Russia ceased production, after more than 11,000 had been produced. From then on, if you wanted a MiG-21 you had only one source, the Chinese J7. In the last three decades China kept improving the J7 capabilities, mainly through tweaks to the airframe and better electronics. Most J7s were used by China but about twenty percent were exported to fourteen countries. About a dozen of these nations still operate their J7s.
Two years ago China officially withdrew its J7s from first line service. This came as no surprise. In the four years before that China more than doubled the number of modern combat aircraft (J-10, J-11, Su-27, Su-30, and J8F) from 500 to over 1,200. Six years ago China relied mainly on some 2,000 locally built copies of Russian MiG-19s (J6) and MiG-21s (J7). There are still several hundred bombers that are mostly Russian knockoffs. Normally, the actual number of Chinese aircraft is a state secret. However, thanks to the ability of Chinese to move freely throughout the country and access to the Internet it's possible to locate and count all the air force units in the country. That shows a current force that is rapidly changing from one that is mostly MiG-21s and MiG-19s, to one composed of much more capable aircraft. China is buying and building a lot of the Russian Su-27s and Su-30s (the latter an upgrade of the former). But new, home grown designs, like the J20 are also showing up.
Another reason for withdrawing the J7 to secondary regions (where modern jets are unlikely to be encountered) is the inability to use J7s for a lot of training. That's important because China is revising its combat pilot training program. The existing system takes ten years of academic and flight training. The new program cuts that to 5-7 years, while increasing flight hours by over 40 percent. This is more in line with Western methods, while the existing system owes more to the one the Russians developed during the Cold War. The new system puts more emphasis on trainee pilots demonstrating combat flying skills before they can graduate. Cold War era Russian aircraft designs, like the MiG-21, were not designed for the heavy use required for Western style pilot training. Thus J7 pilots cannot easily be trained to the same standard as those flying more modern aircraft.
The new training program is actually an evolution of the need for new training methods to prepare pilots to handle the more modern aircraft. Training for pilots of these new fighters has been more intense than for any previous aircraft. In addition, China is also holding training exercises directed at fighting other modern fighters, like those flown by Taiwan, Japan, and the United States. China is not keeping much of this secret and that is apparently sending a message to potential foes.
China has long been the largest user of the MiG-21/J7. China continued to export J7s until this year but has been rapidly retiring the ones remaining in Chinese service. The J7 was, in many ways, the most advanced version of the MiG-21, as the Chinese kept improving their J7 design. Over 13,000 Mig-21s and J7s have been produced in the last sixty years, making this the most widely manufactured jet fighter of the last century (during World War II there were several propeller driven fighters that were produced in greater numbers). The MiG-21 looked fearsome but it was a bust in combat, getting shot down more often than not. Russia still had 186 Mig-21s in service when the Soviet Union dissolved in 1991. These MiG-21s were officially retired a few years later. India, the last major user of the MiG-21, is in the process of retiring them as well.