I'm preparing for a trip to France, and the main though not the only reason is to work on my French and be around it as much as I possibly can before I leave, and I thought why not start early and hitch a ride on a French carrier that does international flghts, am I more likely to hear French from flight attendants and whoever it is that pops on the intercom during a flight? (be it flight attendant or pilot) or is it mostly going to be English?

They will likely use both English and French.

 

Happy Flight.

My experience is they will speak the native language of the flight crew/orgin, the language spoken at the destination (usually), and English. I live in Germany and all my flights within Germany the flight crew made announcements in German and English. When I fly back to the states (usually on Delta) the flight crew makes the announcements in English then in German. When I flew to Tokyo from Vienna on Austrian Airlines they made the announcements in German, English, and Japanese.