Special services may be rendered, or special facilities may be provided on such terms as the city may prescribe from time to time. No person shall use the airport as a base for the carrying on of commercial activities, for the carrying for hire of passengers, freight express or mail, for instruction in aviation in any of its branches, for the sale of fuels, refreshments or any commodity, or for any other commercial purpose, unless written permission or license to do so has been granted by the city. (Prior code § 4.02.023)