(Spirit employee)

BWI was the next Spirit base before Covid, IIRC, it was confirmed by the company. But that obviously never happened.

There was a rumor circulating for a bit that SJU was also slated to be a base. THe purpose being that SJU would be a staging point to take the XLRs to places in South America that couldn't be reached from Florida. Makes sense on paper, but we also opened MIA as an international hub and scrubbed all international flying from MIA a year later, so who knows?

Point is, either of those would appear to be logical for Frontier.