I use the Plat card on a regular basis to gain entry into CO Prez Clubs. And most of the time they also ask to see a ticket.

On my last flight, I used my Plat card to get into one of the IAH Prez Clubs. When the agent scanned it, I specifically asked her if that was to verify the validity of the card, or if it was for CO to get reimbursed by Amex. She said it was the latter.

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In Economy...no one can hear you scream!