The fact that your current itinerary only allows two days pre- and post-cruise is a major problem. The way to leverage the time and money invested in overseas flights is to stay in Europe longer. Although I will tell you that those Adriatic ports on that cruise are spectacular. Maybe do some comparison shopping with Celebrity Air. They will generally have better deals than booking directly with the airlines, but it is important to comparison shop. Where you get the real bargains is on the open-jaw tickets--flying into one airport and returning from another. On a couple of cruises I took starting in Barcelona and ending in Venice, I saved over $4,000 on the return trip from Venice (used miles for the trip to Barcelona).