Received by email:
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In your response to your query:
I am trying to leave one day earlier. same destination. same departure.
everything else is the same with plenty of "cheap" class seats on all flights.
Thank you.
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If you're comfortable that the flight won't fill up, you may be able to stand-by. I don't know AA's rules on different day standby - you need to check these. Otherwise, or if you want to confirm your switch, you could try pleading that you made an error when ticketing (esp. if you bought online), but you're probably going to have to pony up the $100.
There's an interesting discussion on this on the Delta board:
http://www.flyertalk.com/forum/Forum21/HTML/003829.html
Even thought this may be the "right" board to ask, you may have better luck on the AA board with AA experts.