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This isn't merely a technical issue, but an inevitable result of internationalization.
A fighter jet encompasses a vast array of technologies and materials, and the manufacturing materials alone are numerous. Many materials are not produced by domestic companies, and it is impossible for all materials to be produced domestically.
The same is true for the internal equipment of fighter jets, with many components being produced by foreign companies.
This is normal.
If all technology and materials were to come from domestic companies or were to be independently developed, not to mention the time and human resource costs involved, the manufacturing cost alone would be much higher.
Internationalization has a benefit, reducing the manufacturing cost of complex equipment.
For instance, the production of an ordinary mobile phone requires the participation of dozens of countries.
Why involve dozens of countries instead of just one handling everything?