I do not know how to find that. Expert Flyer syas this about IATA fares:
The YY airline is a generic term meaning that the fare is a generic IATA fare. IATA is the International Air Transport Association and posts fares into the reservation systems that airlines have the option of using or not. Click on View Rules to view the details of the fare and remember to contact your airline to find out if they offer the fare.
In searching for RIO to THR under fares I see a YY fare for TAM that is $4,348 one way.