Old Apr 27, 19, 5:36 pm
  #4  
mia
FlyerTalk Evangelist, Moderator: American Express, Citi, Diners Club, Signatures
 
Join Date: Jun 2003
Location: Miami & London
Programs: AA & Marriott Perpetual Platinum; HH Gold
Posts: 38,880
The access rules for Centurion lounges are American Express rules. The access rules for Skyclub lounges are Delta rules, even when using a American Express cards as the admission credentials. The Delta rules are here:

https://www.delta.com/us/en/delta-sky-club/access

Scroll down to find the relevant section. The Virgin flights do not appear to qualify , but the connecting flights to Jacksonville do qualify. You will need to pay to admit anyone who does not hold a Platinum card,
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