(a)
Under regulations prescribed by the Secretary concerned, a member of a uniformed service who—
(1)
is stationed outside the United States; and
(2)
voluntarily agrees to extend his overseas tour of duty for a period equal to at least one-half of the overseas tour prescribed for his permanent duty station;
may be paid the transportation allowance described in subsection (b) for himself and each dependent who is authorized to, and does, accompany him.