A day pass is $59, membership is $600 annually. You can get a discount rate or even comped with different credit cards.
The Barclay's citi bank card
I have been flying a lot lately and have found all Admiral clubs open. The Flagships session (usually reserved for International flights) are not open (as of last week). Besides buying a day pass or annual membership, you can get Citi's "black" Advantage AA card at a +/-$500 and then you can get in as long as on that day you are flying American.
Not all lounges are currently open, and some still have covid hours so check in advance depending on which terminal you are in/what time you will be there. As Chris stated fly 1st/biz on American or a one world partner airline, day pass available if flying American or one world partner. Otherwise visit an independent lounge (priority pass, etc), or visit centurion lounge if you have an AMEX.
There's a credit card that comes with membership or fly business/ first. There are day passes as well
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