(1) An aerial advertising authorisation must be in writing.
(2) An aerial advertising authorisation is subject to any terms and conditions which the Secretary believes are reasonable to impose including but not limited to—
(a) the duration of the aerial advertising authorisation;
(b) whether the aerial advertising authorisation applies generally or in specified circumstances;
(c) whether the aerial advertising authorisation applies to a specified person or persons or to a specified class or classes of person;
(d) whether the aerial advertising authorisation applies to a specified type of advertising or to a specified class or classes of advertising.