Why RDU to MHT? Simple. They don’t fly to BOS and they wanted to add service to the Boston area. BOS charges high fees. They’re a low cost airline with only 15 planes.

I guess the question is, why MHT over PVD? My guess is that MHT is probably pretty desperate to get more business, so it doesn’t die a slow death like ORH is currently. Also, it’s a differentiating factor. They’re the only ones flying this route now. Southwest already does PVD to RDU. Moreover, any new destination for a pitiful airport like MHT gets noticed.