Before the research and development of J 10, China did not independently design aircraft according to American standards, and all of them were imitations.

On the one hand, J 10 needs to be developed, and at the same time, it needs to build a new design system in an all-round way, so it took 18 years to build the prototype.

This time includes the initial theory and conceptual design.

J20 actually took a long time. After the design of J 10 was completed, Song began to do pre-research with reference to his paper "Design Ideas of a Small Aircraft".

From this, we can find that the time of J20 is not short.

On the other hand, after so many years of accumulation, the public relations of the face system has been completed, and the research and development is a matter of course.