The Times are moving forward, the design concept of J-20 is fundamentally different from the design concept of F-22, J-20 considers more supersonic cruise and long range, which is also the development direction of the next six generations of aircraft. In the future air combat, high-energy weapons will be an important direction. If the JF-17 needs to keep up with the pace of future air combat, it will have to introduce high-energy weapons, and high-energy weapons need powerful engines, if it is a twin-engine WS-19, then the energy is enough. But the JF-17 can only be fitted with one engine, and its best choice is the WS-15.