Last time I flew it offered I could upgrade to 1st class for $90 (DFW-MDW). I'm trying to complete a Gold challenge and realized I won't make it unless I fly first at some point in my next trip. My flight out (Sun. 6:35a DFW-PHL) has a ton of first class seats available (11)....so just wondering if I get there early enough if I might get that chance to upgrade again.