I’m a little worried I’ll get bored in Milos. My husband likes to stay in one place, but I like exploring. We would have split our time more evenly but we want to stay on the caldera and it’s just too expensive to stay any longer than two or three nights. Alternatively, we could stay in Santorini for longer but move to a cheaper hotel. Perhaps Santorini 6 nights and Milos 6 nights?
Since airline reservation requests are often made by city-pair (such as "show me flights from Chicago to Düsseldorf"), an airline that can codeshare with another airline for a variety of routes might be able to be listed as indeed offering a Chicago–Düsseldorf flight. The passenger is advised however, that airline no. 1 operates the flight from say Chicago to Amsterdam, and airline no. 2 operates the continuing flight (on a different airplane, sometimes from another terminal) to Düsseldorf. Thus the primary rationale for code sharing is to expand one's service offerings in city-pair terms to increase sales.