Section 15
SEC. 15. Whenever any of the oils mentioned in section one hundred and forty-two of Commonwealth Act Numbered Four hundred and sixty-six are, during the period of five years from the effective date of this Act, used in aviation, fifty per centum of the specific tax paid thereon shall be refunded by the Collector of Internal Revenue upon the submission of a sworn certificate satisfactory to him proving that the said oils were actually used in aviation.