China doesn't announce delays so who knows what has been delayed, stuff like the WS-15, H-20 are likely heavily delayed big ticket items.
I don't think the H-20 is heavily delayed due to staffing issues.
I suspect the original mission requirements (up to the 2nd Island Chain) have been superceded, as this will now be covered by a combination of J-36 air superiority aircraft and the GJ-X unmanned stealth bomber (which is the same size as the B-21 manned stealth bomber).
Note that the J-36 and GJ-X development programmes must have been started before 2022.
So I doubt they even bothered assembling an H-20 airframe designed for the 2nd Island Chain.
And they're now pivoting to a H-20 airframe designed for 3rd Island Chain distances (Hawaii, Alaska, Seattle, etc)
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Engines programmes are in another class altogether. Clean sheet engine development programmes typically take longer to develop than an actual fighter jet.
US has the best aircraft composite materials technology in the world and access to the best materials to build those composites.
Hexcel say they are the only supplier of carbon-fibre to the F-35, with a T800 equivalent carbon fibre.
China can mass produce T1000 carbon fibre now.
So I wouldn't be surprised if Chinese fighter jets start using T1000 carbon first, given the slow speed of future US fighter development.
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Sinofibres can also produce T1100, but I suspect it isn't worth mass-producing in China because it is significantly more expensive and there isn't currently demand for lots of T1100.
No one knows how big the gap between engines are and there are other key technology related to engines like stealthy augmenters, exhaust design etc that China has not shown any mastery in.
I recall a Pentagon/USAF comment that it is only a 10% thrust difference between Chinese and American engines.
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In the current battlespace, I think further improvements in X-band stealth (stealthy augmenters, exhaust design etc) only result in very minor benefits for fighter-sized aircraft. Far more important will be the electronic warfare space, which favours greater numbers of EW platforms and CCAs. Plus the Chinese Air Force expects to have numerical superiority and to be the one with the initative conducting offensive missions in the Western Pacific, so rear-aspect stealth should be secondary.
My guess is that future air battlespaces will comprise very large numbers of aircraft, mostly comprising CCAs of one sort or another. So again, the benefits of additional rear-aspect stealth would be very minor.
However, broadband stealth for fighter-sized aircraft against UHF/VHF radars is still very relevant, and on that front, China is significantly ahead.