1. Regularly scheduled aircraft operated by an air line company for the primary purpose of carrying persons or property for hire in interstate, intrastate, or international transportation.
2. Aircraft owned and held by an aircraft dealer solely for purposes of sale.
3. Aircraft owned by a nonresident who operates aircraft for a period not in excess of ninety days in any one calendar year, provided that such aircraft are not engaged in any intrastate commercial activity.
4. Aircraft owned and operated exclusively in the public service by the state or by any political subdivision thereof, or by the civil air patrol. The amount, manner, method and mode of assessing, equalizing and levying such license tax and the distribution of the proceeds therefrom shall be prescribed by law.