4Terms of enlistment
(1)The term for which a person enlisting in the regular air force may be enlisted shall be such term, beginning with the date of his attestation, as is mentioned in the next following subsection.
(2)The said term shall be—
(a)where the person to be enlisted has attained the minimum age for man's service, such term not exceeding twelve years as may be prescribed, and
(b)where he has not attained the minimum age for man's service, a term ending with the expiration of such period, not exceeding twelve years, beginning with the date on which he attains the age of eighteen years, as may be prescribed,
and shall be either a term of air-force service or a term being as to such part thereof as may be prescribed a term of air-force service and as to the remainder a term of service in the reserve.