I feel nintynine's pain. If only there was an airline with no change fees.
I've only discovered two, neither will work for 99.
Frontier -- if you hit their top level status (Summit) which is 30 segments in a year. That would be easy for 99, but they don't fly from MCI to either ORD or MDW. No scheduled service through DEN and who'd want to do that?
Allegiant -- Pay $8 for trip flex per segment. However, you can't cancel in the last 24 hours. Also no good for 99 because they primarily go to to LAS, PHX and Orlando Sanford.
UA and AA have a huge opportunity at this moment to kill their change fees, or at least do it for their 2P/Silver and above. But, I'm sure they won't seize the moment.