Posting this because I found the info pretty unclear beforehand. Yesterday my partner flew Alaska out of JFK in an upgraded First seat and I sent him one of my Alaska lounge pass codes to try at the AA Admirals Club in Terminal 8.
He showed his boarding pass, mentioned he had an Alaska lounge pass code, and was let in without any issues. Super smooth.
I was confused going into this because Alaska flyers in First can use the JFK Admirals Club on longer flights, but it seemed like that only applied to paid First, not GGU or U class upgrades. Since Terminal 7 is gone, this lounge is basically the replacement.
Anyway, just wanted to confirm that Alaska lounge passes do appear to work at the JFK Admirals Club if you’re flying AS out of T8.