Mikoyan-Gurevich MiG-21 (USSR) ✈ Chengdu J-7 (China)

Mikoyan-Gurevich MiG-21 (USSR). First flight: 14 February 1956 (WIKI)

Chengdu J/F-7 (China). First flight: January 1966 (WIKI)

Soviet Premier Nikita Khrushchev unexpectedly wrote to Mao Zedong in February 1962, to inform Mao that the Soviet Union was willing to transfer MiG-21 technology to China [...] The Chinese viewed this offer as a Soviet gesture to make peace, and they were understandably suspicious, but they were nonetheless eager to take up the Soviet offer for an aircraft deal. A delegation headed by General Liu Yalou, the commander-in-chief of the People’s Liberation Army Air Force (PLAAF) and himself a Soviet military academy graduate, was dispatched to Moscow immediately, and the Chinese delegation was given three days to visit the production facility of the MiG-21, which was previously off-limits to foreigners. The authorization for this visit was personally given by Nikita Khrushchev, and on March 30, 1962, the technology transfer deal was signed. However, given the political situation and the relationship between the two countries, the Chinese were not optimistic about gaining the technology, and thus they were prepared for reverse engineering.
— Wikipedia

Sukhoi Su-27 (USSR) ✈ Shenyang J-11 (CHINA)

Sukhoi Su-27 (USSR). First flight: 20 May 1977 (WIKI)

Shenyang J-11 (CHINA). First flight: 1998 (WIKI)

The J-11 was finally born in 1995 as a Chinese version of the Soviet-designed Sukhoi Su-27SK air superiority fighter after China secured a $US2.5 billion production agreement which licensed China to build 200 Su-27SK aircraft using Russian-supplied kits. Under the terms of the agreement, these aircraft would be outfitted with Russian avionics, radars and engines.
— Wikipedia