N.D. Cent. Code § 57-32-02
The tax commissioner, after the provisions of chapter 57-06 have been complied with and final assessment has been made by the state board of equalization, shall compute a tax upon the valuation fixed as is provided by law for the assessment of other utilities. Such a tax must be computed by applying to that portion of the valuation which by law is subject to tax the average millage rate, which is obtained by dividing the total taxable valuation of all property within this state for the current year, into the total of all state and local taxes assessed within the state on a millage basis for the current year. The tax for air transportation companies must be computed by applying, to that portion of the valuation which by law is subject to the tax, the average millage rate which is obtained by dividing the total taxable valuation of all property for the current year, within all cities operating an airport served by scheduled airlines in North Dakota, into the total of all state and local taxes assessed within all such cities on a millage basis for the current year.
N.D.C.C. § 57-32-02