All* bookings made directly with Air France can be cancelled for free within 24 hours. If cancelled before midnight in the timezone of purchase, it is likely that the money will not be taken for payment. If cancelled past midnight, you will likely see the money taken, and refunded some time later.

Warning: You should never rely or depend on this 100%, i.e. DO NOT adopt a strategy where you knowingly book a ticket with the full intention of cancelling within 24 hours. There will always be times where either the website isn't working, or the call centre can't be contacted, and you will end up stuck with a non-refundable ticket.

Note also that bookings made via third parties (including Flying Blue!) cannot be cancelled for free via this channel, and will be entirely the responsibility of the agent with whom you entered the contract. They will, almost certainly, not allow a free cancellation despite this being possible if you had instead cut out the middleman and dealt directly with Air France.

US website: https://www.airfrance.us/cgi-bin/AF/...BOOKING_REFUND
FR website: https://www.airfrance.fr/cgi-bin/AF/...BOOKING_REFUND
GB website: https://www.airfrance.co.uk/cgi-bin/...BOOKING_REFUND
AE website: https://www.airfrance.ae/cgi-bin/AF/...BOOKING_REFUND