In the 1990s, China introduced the Su-27SK fighter from Russia. Compared with other fighters of the air force, the Su-27SK is characterized by high fuel carrying coefficient and long range. Due to its large body space, it can be equipped with more avionics systems and weapons. The most valuable thing is that it can still maintain a combat radius of thousands of kilometers when four medium-range air-to-air missiles are hung on the belly and two combat missiles are hung on the wing tip, In other words, it can reach a far theater for operation, or stay in the theater for a long time, so as to reduce the blank period of air cover caused by poor endurance and frequent rotation of fighters. This is also the main reason why the traditional former Soviet airmen who operate light and flexible fighters with low range also chose the Su-27.