Another little fact that DL (or just about any other airline) doesn't disclose on these "though flights" is the fact that sometimes regular connecting flights are available with shorter layovers, lower fares, full FF miles flown, and upgrade possibilities on the domestic segments. In many of these cases, it is necessary to connect through a different hub, but not always. If you're going to be dealing with the "equipment change," shuffle, you might as well get something good for your trouble. Always check out ALL the options for getting from point A to point B, and not whatever comes up first on the search engine, as rcherskov so aptly suggested.