For the purpose of acquiring and improving an aviation field, any such county may issue and sell bonds of such county to be designated aviation field bonds, to provide the necessary funds therefor. Such bonds shall become due in not to exceed twenty years from the date of issuance, and shall draw interest, payable semiannually or annually. Such bonds may not be sold for less than par, and in no case without the proposition of issuing the same having first been submitted to the legal electors of such county at a general or special election held therein, and a majority of the votes cast upon the question of issuing such bonds being in favor thereof. The authority to sell such bonds shall not be limited by any other or special provision of law.