Why do MiG-29 and Su-27 look the same?

The MiG-29 and Su-27, both iconic Russian fighter jets, have some design similarities because they were developed around the same time to fulfill complementary roles in the Soviet Air Force. Both aircraft were developed in response to the American 4th generation fighters, mainly the F-15 and F-16, and share a common design philosophy emphasizing speed, maneuverability, and versatility.