Do you mean what airport or what terminal? Check Frontier's website for airports and RSW's website for the terminal.
You can see all their service areas on their website
To see all the nonstop city destinations that Frontier Airlines offers from Southwest Florida International Airport (RSW), see the RSW Air Service Update at https://flylcpa.com/airservice/. To see all route options for Frontier Airlines, system wide, visit their website at https://www.flyfrontier.com/.
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