In France, the following are two of the main ways people get promoted in academic positions:
- Maître de Conférences (assistant professor whose responsibilities include teaching as well as research) -> professeur (professor)
- Chargé de recherche (in charge of research) -> Directeur de recherche (director of research).
Note that in the second sequence of academic promotions, one doesn't have to teach and the positions are mostly dedicated to research (although one can opt to teach if s/he wants to).
My question is: while applying to a position (postdoc/permanent) in the team of a chargé de recherche where s/he is the PI of the project, should one address her/him as a professor ("Prof."), say in the cover letter? It's technically incorrect it seems, but perhaps no harm is done because their positions are equivalent to those of professors anyway.
I'd like to know the viewpoint(s) of someone(s) who's familiar with the French system!