Sorry for the wrong vocabulary, I am not someone from the aviation industry.
There was an incident (?) in a Foker 100 in Australia. Let's now imagine that there is some project change that has to be done. Foker is out of business for years now, who is responsible for doing this change? And paying for it?
A similar question also applies: where do aircraft parts that have to be substituted come from, so planes are still able to fly?