|Subject: Re: Airline upgrades|
Not exactly an upgrade, but a couple of suggestions. These only work part of the time, but if they do, you get more space, and don't have to use miles or dollars.
AA has more space in most Economy sections, but yu appear to want to fly on US Air. If you are flying on US, you might check to see if you are actually on a United code shared flight. UA has the front section of Economy with extra spacing. On United, elites get first choice of the extra space seating, but any open seats in the extra space section that have not been assigned are available generally on date of flight.
Also, on most airlines, seats in the exit rows are not assigned until day of check-in, since the airline is supposed to check that you are fit and able to open the doors and such. If you get there early enough, you might be able to grab an exit row seat.