Cheap flights to Europe from Chicago and Quito, Ecuador?

I want to travel around Europe for about 2 months from the late June/Early July to late August/Early September. I'm flying from Chicago but my cousin is flying from and returning to Quito, Ecuador. Does anybody know a cheap airport in Europe for both of us to fly to? It doesn't really matter where in Europe, we're going to get Eurail pes and travel around. Thanks!