I'd suggest looking at that "mixed" itinerary very carefully before booking. When it says "mixed" on delta.dumb, it could mean that some of the flights are called FC and some are called business class, but other times it means that one or more of the segments will be in coach. You need to click on all the details and look at everything very carefully before purchasing the ticket. [If it were DL only, I'd tell you to look at the one letter class codes, but they can be different on other airlines.]