Welcome to FT! From just a cursory view of your post, I can tell you that US Air will be the best airline of choice. As its a secondary hub for them, rates are usually very competitive from PHL. As an AA LT member, I'm most looking forward to US Air's integration into AA later this year/early next year. That said, as a UA person, you may have to abandon your Star Alliance proclivity for what will probably be a One World takeover of the PHL market.