May be worth calling and seeing. Could be something wonky with their systems, as with DL outbound the return should be DL marketed, even if Amex is showing the AF marketing. But whether they still code it as DL is a question.
Originally Posted by
friedablass
No, it's not considered 2 separate one ways from what I can see in replicating what the OP is trying to do. As I mentioned above, DL and AF are partners and do codeshares so on Amex travel it is possible to select DL marketed flight on the outbound and AF marketed on the return and pay the roundtrip price. On Amex Travel once you select the outbound flight on a roundtrip itinerary, the only options I am ever shown for the return is on the same airline or codeshares as I chose for the way out and is eligible to buy as a roundtrip fare. For example, once I chose a DL flight (or DL marketed) going from US to Paris, all the return options are only DL or AF (marketed) flights. I am not shown any options with Virgin or Swiss or BA or UA or anyone else which would certainly indicate separate one ways.