Authorities created under this act shall plan, acquire, construct, operate, maintain, replace, improve, extend and contract for public transportation facilities. An authority is a public benefit agency and instrumentality of the state with all the powers of a public corporation, for the purpose of planning, acquiring, constructing, operating, maintaining, improving and extending public transportation facilities, and for controlling, operating, administering and exercising the franchise of such transportation facilities, if any, including charter operations as acquired.