Vancouver is adding a nonstop flight to New Zealand partly because the expanded international terminal at YVR makes the city more attractive to carriers, according to today's Wall Street Journal ($).
The flight used to stop in Los Angeles but that airport is losing international flights because of its old, crowded international terminal. A similar story could be told about the rivalry between SEA and YVR.
The issue is about more than a handful of flights, as the WSJ puts it:
The stakes are high for cities. International passengers spend about twice as much as domestic travelers, and international airline service is one important competitive benchmark for cities competing for corporate relocations
Vancouver, which recently expanded its international terminal, is already wooing travelers from the Seattle area. Since significant improvements at Sea-Tac are years away, it has to rely on cutting fees to lure airlines, which is how it won a nonstop flight to Paris.