...what does Chinese gain from these attacks then? International infamy?
Valuable aviation intel to use for their young, but growing, airline industry.
Makes me wonder if it'd be simpler to gain this stuff the old-fashioned spy way: bribe or blackmail someone working in one of those supplier companies.
If Pierre in Toulouse is desperate to hide his affair with the Chinese girl he met a week ago in the bar...
Oh, that certainly happens as well. It's just harder to pull off, because physical security at these companies (even physical computer security) is well ahead of network security.
Or the other way: just buy it outright. Either buy from the supplier companies, or buy existing stuff used and reverse-engineer it.
This isn't denial of service attack, this is unauthorized access to steal technical data.
I wouldn't call it cyberattack then; rather it should be cyberespionage
Stealing blueprints and other technical data so they can make their own knockoffs of western aircraft, as they have with the J-20 (F-22 knockoff) and J-31 (F-35 knockoff).