In the era of third- and forth-generation aircraft, the aerodynamic layouts of fighters in various countries are very different, such as the light MiG-21, the MiG-23 with variable swept wings, the F-104 with short and thin wings t(hat can cut even vegetables), The F-4 that ditched the cannon, the slender Su-27, the handsome F-14, and the F-15 of Lida Flying Brick, the F-16 that looked perfect from any angle, and the angry super hornet F/A-18, the shape has its own characteristics.
However, in the era of the fifth generation aircraft, except for the Russian Su-57, Su-75, and China’s J-20, the designers of other aircraft seemed very similar spacially from the front view, and the products they came up with looked so much like the F22 and F35, such as South Korea’s KF-21, Turkey’s TF-X, India’s AMCA, and China’s FC-31, why is this?
First of all, due to the need for stealth, the space available for the aerodynamic layout of the fifth-generation aircraft is indeed very limited. The first condition for stealth fighters is to be invisible in appearance, and to achieve invisible appearance, the basic principle of parallel wing and fuselage edges must be followed. Since then, many good aerodynamic layouts will inevitably be limited, and F22 and F35 are currently The most balanced solution for the situation.

Secondly, behind any aerodynamic layout, there must be a deep accumulation, even decades of foundation. In terms of hardware, at least there must be a large-scale wind tunnel and power supply, and enough blowing tests can be done to find out the aerodynamic layout that suits you. And this basic condition is almost completely absent from South Korea and Turkey. India has a little foundation, but only a little bit. Therefore, in the case of such congenital deficiencies, the safest and most convenient way is to directly copy F22 and F35.
The key point is that if you really copied F22 and F35 directly, it would be fine, but the fear is that in order to highlight own national characteristics, country change a little here. It is the most troublesome, just like the Chinese-made fighter aircraft J-10. j-11 and J-16.
Third, there is a certain mentality of worshiping the United States in these planes. The high technology of the United States is good, so if I make a shape similar to the United States, maybe I can borrow some of the “magic power” of the F22 and F35.

In fact, they are not the first wave of people with this kind of “fanaticism”. As early as when the United States developed the F22, Germany, Sweden, and even Brazil and Argentina proposed their own fifth-generation aircraft plans, but in the end, they all correctly recognized their own strength and retreated. I believe that in the future Turkey and South Korea will also retreat in spite of difficulties. But India surely get the success, country defence industry maturing in fast lane and already made LCA Tejas which is quite good and far better than S. Korea T-50 and Turkish Hurjet.
Of course, as the saying goes, “Dream is always there, what if it comes true?”, as long as you want to develop a fifth-generation machine and make up for the foundation of the third- and fourth-generation machines first, if you make persistent efforts, your dream will come true.
But the problem is that by then, the sixth-generation aircraft may be flying all over the sky, and the fifth-generation aircraft will fall behind as soon and a lot of manpower, financial resources, and material resources will be wasted in vain.