And why would you want to know that?

Whether someone here confirms it or not for their own travels, the fact of the situation is that people do travel on intra-Scengen flights with expired Schengen visas, expired residence stickers/cards or with passports having stamps that make it seem like they have been in the Schengen zone for more than 90 days within any 180 day period. If any or all of that is a problem during the course of intra-Schengen travel by air, it's a very infrequent problem for persons in such categories.

You're absolutely correct, but the opposite is also true (intra-Schengen flight: my sister was denied boarding because her Schengen-country passport (!) had expired three days earlier). I guess there are explicit rules somewhere, but a) there are strict check-in agents, b) there are laissez-faire check-in agents and, unfortunately, c) there are stupid check-in agents; in brief you'll hear all possible outcomes from travellers, frequent or not, who faced situations.

Your sister's example is an example of an expired passport and is quite distinct from a situation of having a valid passport with expired visas, expired residence stamp/sticker, expired residence cards, or stamp-situation indicating possible overstay.

I like the characterization of how it goes with check-in agents. And yes there are indeed various possible outcomes, some outcomes far more probable than others and varying based on the involved factors.

hello back all

also like to point out that tight passport checks are perfomed mailny on citizens of coutries
that requires a visa to travel to schengen area ;

What do you mean by tight passport check? A CI agent can only look at the validity of the passport and, for non-Schengen citizens, the validity of the visa (not even certain about the latter). A CI agent doesn't have the power of police and since you don't need a passport (or a visa) to travel intra-Schengen, (s)he only needs to verify the identity!