What is known is that given its size, the twin-engine J-20 will most likely serve as a strike fighter, like the F-111 Aardvark, rather than as an air superiority fighter. The J-21 would serve as an air-superiority fighter.
As China develops two new 5th generation fighters, this is in stark contrast to America's F-22 and F-35s that have had issues with oxygen sensors and budgetary issues.
China's new planes also have their own problems, namely their Russia made engines, a potential 'Achilles Heel'."
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