Be careful though with the W fares and booking on DL.com - I have fallen for that once. While the fare restrictions on AF for my selected dates and flights allow changes, etc. (against a fee), the respective DL-fare does not. I ended up with a non-changeable, non-refundable W ticket on DL that was more restrictive than a T-fare (which also was $1k cheaper).
Was the DL W fare the same price as the fare you saw on airfrance.us? Generally DL will publish a W fare at the same price as AF's A fare, which is the restricted, discounted PV fare.