I would consider English skills to be pretty essential for customer-facing staff on an international airline. I mean in the case of the OP we're talking a CDG-FRA flight, so some have said "why would they speak English on a flight between France and Germany?"

Now first of all, I'll believe that all of those crew members were fluent in German when I see it as it's far from likely. And aren't both of those airports major hubs, aren't both cities home to major businesses? On those flights there's always going to be passengers from outside France and Germany. Should people connecting FRA-CDG-ATL be expected to learn French because they chose to give their money to Air France? That would be classic French pride over business sense.