Originally Posted by
MSPeconomist
You might want to consider trading your AmEx DR card for the regular AmEx Platinum Charge Card (not the AmEx Delta Skymiles Platinum Credit Card) for about the same annual fee. You would get Membership Rewards points on total spend rather than DL Skymiles. This gives you DL SC access when flying DL same day and CO PC access when flying CO same day, including two guests. The same holds for a thrid airline--I think it's currently AA. Note that codeshares do not count.
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Not anymore - CO cut off Amex Plat from their club as they moved forward with the UA deal.