It's FFCHI + FFD + FL + 3B + AL "where available"
From AA:
With Flagship Business Plus, customers can enjoy Flagship First Check-In, receive a taste of our Flagship First Dining and relax in our Flagship Lounge prior to their departure.
Flagship Business Plus also provides a third complimentary checked bag and access to the Arrivals Lounge at LHR.
Cheers !