The simple economics is in passenger volume. A plane can carry more people, to more destinations within Europe, several times a day. Your statement that "As fa

The simple economics is in passenger volume. A plane can carry more people, to more destinations within Europe, several times a day. Your statement that "As far as I know, for example, trains are significantly more fuel efficient per passenger-mile" definitely has some merit, but... trains are only more fuel efficient per passenger if they are as full as planes. An Airbus with 180 passengers might beat a train in per passenger miles if the train is not loaded. Considering that, trains definitely are cheaper for highly utilized routes (commuting routes, for example), but for a leisurely trip across Europe, an Airbus packed to the gils could be cheaper.