Some guest access info from AA.com:
Citi Prestige Card holder 2 Guests or immediate family*
Citi Prestige Card holder must present a stand-by ticket or boarding pass (other than a non-revenue ticket or boarding pass for airline employee travel), showing an American, American Eagle Airlines, Inc., or an American Connection carrier flight number, valid for travel on such flight and departing within 12 hours of the Admirals Club visit (or, in the case of a visit at an arrival airport, with respect to such a flight that arrived no more than 12 hours prior to the visit.)