Initial question did not state which airport (I think there's more than one in Pennsylvania). Allegheny County, when they created the Pittsburgh Airport Authority, included a "no guns" section in their ordinance. Both the PIA and Allegheny County Police websites state you might be arrested and guns are prohibited on airport property (not just the secured areas). See the discussion on Open Carry dot Org
here.
Haven't heard of anyone being busted for carrying, but Allegheny County, the airport operating authority, and the county police have all be notified that any such ordinance is illegal by state law.