I will prefix by saying that most of my flying to/in the USA is done on Delta.... Business Elite on Delta is very good and I believe they serve more destinations in Europe than any other US airline. However, ATL and CVG are not always convenient as hubs (ATL is a long way from Seattle). DL does offer quite a few flights to Europe from JFK. On the domestics, CVG is a great airport for connections and ATL can be tough because of its layout and because it is so busy.