The Assistant Adjutant General for Army shall be the chief administrative assistant to the Adjutant General for Army matters and the Assistant Adjutant General for Air shall be the chief administrative assistant to the Adjutant General for Air matters and both shall perform such duties as may be directed by the Adjutant General. In the event of the death or disability of the Adjutant General or any other occurrence that creates a vacancy in the office, the Commander-in-Chief shall designate either the Assistant Adjutant General for Army or the Assistant Adjutant General for Air as the Acting Adjutant General to perform the duties of the office until an Adjutant General is appointed.