The monopoly held on stealth technology by the United States and its allies is nearing its end. With both Russia and China fielding prototypes of fifth generation fighter aircraft, the USAF faces the prospect of facing hostile air forces wielding a degree of sophistication that was unthinkable a few years ago. But why are our adversaries seeking to deploy these weapons systems in the first place? How do they plan on employing them, and what do they hope to gain?
The least likely scenario is that the Russians and Chinese want an “F-22 killer.” The F-22 is the most advanced fighter in the world and shooting down hostile aircraft is both the most inefficient method of offensive counter air and one of the methods in which the skill-gap between the USAF and its potential peer competitors is the widest. Therefore, dedicating fifth-generation aircraft to shoot down F-22s is likely a poor use of resources as it is a relatively high-risk, low-reward use of a valuable commodity.
A more likely scenario is that these planes may be used to seek and destroy less advanced US aircraft. The aging “teen-series” still makes up the majority of US airpower, and even if the latest Russian or Chinese aircraft are not superior to their American equivalents, they should still easily outmatch an F-16 built in the Reagan-era. This seems like a particularly likely use for the PAK-FA, which appears designed for an air-superiority role.
The most efficient means of using a stealth aircraft against the United States, and the most likely use of the larger J-20, is the strike role. Shooting down enemy planes is all well and good, but simply blowing up their airfields is a much more efficient. This is the method favored by the USAF itself whenever possible, as it has the potential to completely neutralize enemy airpower altogether.
Of course, the million dollar question is, why do the Russians and Chinese need a fifth generation fighter in the first place? After all, surface-to-air missiles account for the vast majority of US aircraft shot down in the post Korean War era, and are cheaper to boot. Cruise missiles can destroy American airfields, and are more difficult to shoot down than fighter aircraft. For the purposes of shooting down teen-series aircraft (and probably the F-35 as well, truth be told,) the 4.5 generation Su-35 is more than sufficient. Even when played to its strengths, a fifth-generation fighter is not the most effective means of fighting the US Air Force.
The most likely answer is that by adding another threat which requires different countermeasures than already existing methods of combating the USAF, the Russians and Chinese hope to force the USAF to divert spending from other programs in order to counter the threat posed by hostile fifth-generation aircraft. This would produce a strategic net gain for the Chinese and Russian air forces disproportionate to the relatively small tactical value these aircraft provide.