When I fly, I like to have the aisle seat as I have long legs. My husband likes the window seat so he can fly the wing. We usually end up with a stranger sitting between us. Not that I'm rich-I always fly coach-but I"ve often wished I could purchase that middle seat so that we can have the extra room. It would be nice to stash our carry-ons underneath the unoccupied middle seat, or even stretch out. But I don't think I've ever seen that option when purchasing tickets. Is it possible to buy a third seat without actually having it filled?