You don't do one-way. You price Multi-city and try to stay with one airline or partner. example. My son is flying from DC to Detroit, driving to Toronto, return flight is from Toronto. Flights on Northwest price out the cheapest @ $227. We flew to Amsterdam on KLM and returned from Genoa, Italy (actually Milan) on Alitalia both Northwest partners from Boston. I used American to San Juan and from Acapulco. Do some research on-line and price out each segment individually. Then let a TA price the exact flights you would like to get the best price. For Europe, the cruise line did guarantee the KLM/Alitalia flights at a very good price and we were going to go in a day early anyway, so it was worth the deviation fee especially for the airport transfer in Italy. Milan is a 2 1/2 hr. drive from the port.