Autumn is a great time to visit Europe. The packs of tourist have gone home, the locals are back from their own "holiday," and the heat has subsided. Best of all, that's when fares start to settle down to more reasonable rates. Icelandair is offering shoulder-season fall flights to Amsterdam, Frankfurt, London, and Paris, among others. Departures are available from Boston, New York City, Seattle, and Washington, D.C.