When you buy a ticket on-line, you don't know where you will be seated nor Air France allows you to see it. Only at check-in time, ie 30 hrs before the actual trip, you can view your seat number and eventually buy an option for changing the seat. In our case, it meant that I had to be up at 6:00 am the day before in order to view our seat allocation. Of course, we were assigned seats at the back of the plane and I was "convinced" that I needed to change seat. Of course, the only remaining seats were the exit seats for which you need to buy the option. Why don't we get the possibility of buying seats at booking time?