Originally Posted by
jxwolf
Traveling with my Amex Platinum, I've always had to show my boarding pass, which is usually scanned along with my card.
Admittance to an airline lounge with the Amex Platinum is governed by different rules which as far back as I can remember have always required that you have a same-day ticket with the airline operating the lounge.
The OP refers to actual members of the respective lounges.
(AA,CO,DL,NW) In this case
L/NW.