Ala. Code § 4-5-2
Each county shall have the power from time to time to sell and issue interest-bearing warrants of such county or interest-bearing certificates of indebtedness of such county for the purpose of paying the cost of acquiring and providing county airports, including lands, structures, runways and all other airport facilities whatsoever. Such warrants and certificates may be in such denomination or denominations, may have such maturity or maturities not exceeding 30 years from their date, may bear interest from their date at such rate or rates not exceeding six percent per annum, payable semiannually, may be payable at such place or places within or without this state, may be sold at such time or times and in such manner, may be executed in such manner and may contain such terms not in conflict with the provisions of this chapter, all as the governing body of such county may provide in the proceedings wherein the warrants or certificates are authorized to be issued. All such warrants and certificates shall evidence general obligation indebtedness of the county by which they are issued, and the full faith and credit of the county shall be irrevocably pledged for the payment of the principal thereof and interest thereon. The proceeds derived from the sale of any such warrants and certificates shall be used solely for the purpose for which they are authorized to be issued, including the payment of any expense incurred in connection with the issuance thereof.
Ala. Code § 4-5-2 (1975)