I'm looking to meet a friend I originally met in China (she lives there, I'm from the US), ideally around Christmas. We don't need to meet in China, just anywhere in the world we can both get to that keeps the total cost of both (or just one of) our traveling the cheapest. I've been having a hard time finding services that don't require a predetermined city to travel to. The best I've found so far is Google Flight Maps, but even that has limitations. Does anyone know of something better?