Kidz, depending on the circumstances of the downsizing, you may not have a problem changing to another flight regardless of what class fares are still available for the flight you wish. If the Embraer EMB-145 is overbooked, better yet. If so, I imagine CO will jump at the chance. If necessary, I would explain that you Mother refuses or is unable to fly on anything smaller than a 737 and that the only reason you booked your reservations was due to the 737s.

Good luck.

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