Thank you very much for your advice. In fact all Air France is getting very much like the Aeroflot in the good old Soviet days. This premium Economy in KLM or Air France is not worth the additional payment at all. Air France is also extremely poorly organized: their sales team have no idea how to include the Sky Team Airpasses when you purchase an intercontinental ticket.
I wonder when the company needs to be rescued by French Taxpayers?