An example here is British Airways' service from New Orleans to London. Obviously, some amount of people have always wanted to get from New Orleans to London, but previously they've been flying though Dallas/Atlanta/New York, etc. The 787 allows BA to offer a much better product to those customers, and the size/cost to operate a 787 is what makes the flight commercially viable. When the sky is full of airplanes operating flights like that, there's no one group of people in one place to fill up a jumbo.