N.C. Gen. Stat. § 160A-273
A city shall have authority to grant easements over, through, under, or across any city property or the right-of-way of any public street or alley that is not a part of the State highway system. Easements in a street or alley right-of-way shall not be granted if the easement would substantially impair or hinder the use of the street or alley as a way of passage. A grant of air rights over a street right-of-way or other property owned by the city for the purpose of erecting a building or other permanent structure (other than utility wires or pipes) shall be treated as a sale of real property, except that a grant of air rights over a street right-of-way for the purpose of constructing a bridge or passageway between existing buildings on opposite sides of the street shall be treated as a grant of an easement.
N.C. Gen. Stat. § 160A-273