Looks like the infamous CPH fare to me
You can have one connection here in Europe, on any carrier except those exluded in the fare rules. So you can go (just some examples):
CPH-AF-CDG-DL-ATL
CPH-KL-AMS-DL-ATL
CPH-AZ-MXP-DL-ATL
CPH-LX-ZRH-DL-ATL
CPH-IB-MAD-DL-ATL
CPH-DM-MUC-DL-ATL