Linda wrote in :

Not sure what you mean about "airline overflows," I'm noot aware of too
many planes landing PVD because they can't land BOS. Class C
corresponds to airspace, not the airport itself or FBO services.

PVD has fees but there are less friendly places to fly into.

What I mean is this: Logan is one of the busiest airports in the world, with
extreme traffic, both in the air and on the ground. Numerous people from the
Boston area fly in and out of PVD to avoid dealing with Logan, and so it is
more than just a local class C airport in its own right. It's almost an
extension of Logan.

The same holds true for MDW relative to ORD, and for HPN relative to NYC, BWI
relative to IAD, and SNA relative to LAX...

Contrast this with the Class Cs that are rated as such because they service
cities that just don't quite have as much traffic as a Class B - BDL, SDF,
ACY, MHT, MSN, PWM, PIA, LIT, ROC, etc. In my experience, airports like those
certainly have nice FBOs and charge landing fees, but they are slightly more
GA friendly than the Class C's that are really just extensions for their
Class B counterparts "downtown".