In Reuters: Wing cracks, other flaws delay China jet manufacture we read:
But as leaders of the global aerospace industry gather in Beijing for an International Air Transport Association meeting that kicks off on Sunday, a closer examination by Reuters shows that the potential challenge from China might be greatly overblown, and that its aircraft sector is unlikely to pose any credible competition for at least a decade.
It then goes on to point out that the ARJ21 wings cracked before passing the stress test, that its avioncs is having systems integration and wiring issues, and that the company is not dealing with these issues openly.
Estimates have the ARJ21 about five years behind schedule for getting regulatory approval and the C919 currently around 3 years late (slip from 2016 to 2019), and that the ARJ21's ongoing woes may push the C919 out even further because the C919 certification effort has dependencies on the ARJ21 certification effort.
One stunning comment from Richard Aboulafia about the ARJ21:
"it has turned into an overweight and stunningly obsolete product that has no relevance outside of China's tiny regional airline sector"
But, both A and B are still concerned that at some point Comac may produce a plane good enough for local needs and perhaps beyond, which will of course be something they'd rather not have to cope with.