Say what you will about the F-35, but Lockheed Martin has actually built and delivered one hundred and seventy one aircraft thus far. The Russian Air Force, meanwhile, has yet to receive its first PAK FA. In lieu of the PAK FA, Russia has continued to acquire generation 4.5 fighters (mostly of the Flanker family) as well as upgrading generation 4 fighters (including various Flankers, the MiG-29 Fulcrum, and the MiG-31 Foxhound). Sukhoi will likely never build the number of fighters that Western analysts expected, or that the Russian Air Force wanted.The PAK-FA, also known as the Sukhoi T-50, apparently has major performance problems. Russia can't build this aircraft in economically sustainable numbers without export sales. It would appear that engine performance problems are hurting that effort:
Acquisition of the PAK FA has slowed for two reasons. First, technical problems have beset the program, as Russia’s aviation industry (weighed down by the legacy of the post–Cold War collapse) has struggled with the development and manufacture of advanced stealth and avionic components. Second, the Russian economy has been damaged in the face of a worldwide drop in oil prices, and Western sanctions stemming from the decision to seize and annex Crimea. All in all, it remains unclear whether the PAK FA will ever threaten Western dominance of the skies.
In my opinion, this is not a positive development for the U.S., despite how it might look at first glance. If the T-50/PAK-FA is not a competitive aircraft, then U.S. supporters of the F-35 can start dancing for joy and proclaiming the the F-35 is the best fighter plane around.
First of all, it isn't -- the F-22 is. The F-22 was discontinued because of operations costs, which are dramatically higher than any other aircraft in the U.S. arsenal, including the F-35, and because the military wanted an all-things-to-all-people aircraft. Or maybe Congress did. No longer clear. The F-22 is the finest fighter airplane ever. The F-35 is not designed to be that plane -- it is supposed to be a fighter plane, a tactical bomber, a carrier aircraft, a SVTOL aircraft and God knows what else. Any aircraft that can fill all of those roles will do none of them well. I suspect that is the main problem with the F-35.
If the PAK-FA is a failure, that is not good for the U.S. fighter development program. That failure likely would encourage F-35 supporters to rest on their laurels. The problem with that, of course, is the the F-35 might or might not turn out to be a fine aircraft at this or that of its intended roles, but there is virtually no chance that it will turn out to be a fine aircraft at all of its intended roles, which is all roles for which modern military aircraft are intended.
If the F-35's supporters are able to claim that it has no genuine competitor because the PAK FA is a failure, then the people who decide whether to spend money on fighter aircraft might decide that there is no need to do so on other aircraft, at least for a number of years, because the F-35 is so damn wonderful. The odds of the F-35 being so damn wonderful at all of its roles are close to zero. I have been a supporter of the F-35 as a fighter aircraft. I believe it is a dog-ass replacement for the A-10 as a close-air support aircraft. The F-35 has no chance of performing as well as the A-10 in a close-air role. None. But if the PAK FA is viewed as a complete failure, there is a possibility that the F-35 will be accepted as the default replacement for the A-10, among the other aircraft it is supposed to replace. I don't think that would be a good result.