Let me explain. I want to book a round trip from JFK to CDG. I will fund this by transferring American Express Membership Rewards to my Flying Blue account. The problem is that I don't know how many I will need and I don't want to transfer a large number of miles that may be more than I need.

Is this possible? If so, what is the procedure? I read in this forum of people putting reservations "on hold" but I do not see the option to do that.

Your help would be appreciated.