Section 73.15 - Using agency(a) For the purposes of this subpart, the following are using agencies;(1) The agency, organization, or military command whose activity within a restricted area necessitated the area being so designated.(b) Upon the request of the FAA, the using agency shall execute a letter establishing procedures for joint use of a restricted area by the using agency and the controlling agency, under which the using agency would notify the controlling agency whenever the controlling agency may grant permission for transit through the restricted area in accordance with the terms of the letter.(c) The using agency shall-(1) Schedule activities within the restricted area;(2) Authorize transit through, or flight within, the restricted area as feasible; and(3) Contain within the restricted area all activities conducted therein in accordance with the purpose for which it was designated.