26. In the case of an aircraft which has commenced its voyage at a place within the excepted area and has not during its voyage alighted at any place outside that area—
(a)the commander shall not be bound to comply with the provisions of regulations 11 or 25(1)(a) unless he has been notified by the medical officer that compliance with those provisions is necessary because of danger to public health;
(b)no person carried by the aircraft shall be bound by the provisions of regulation 25(1)(b) or (c) unless he has been notified by the medical officer that those provisions apply to him because of danger to public health;
(c)the powers and duties conferred or imposed on the medical officer by regulations 7, 8(1)(2)(3) and (5), 9, 14(1), 18(2), 20, 21, 22 and 23 shall not be exercised or performed unless the medical officer is satisfied, or the Secretary of State has directed, that the exercise of the powers or the performance of the duties conferred or imposed by those provisions is necessary because of danger to public health;
(d)the powers and duties conferred on a customs officer or authorised officer by regulations 8(3) and (4) and 16 shall not be exercised or performed unless the Secretary of State has directed, or the medical officer is satisfied and has so informed the customs officer or authorised officer, that the exercise of the powers or the performance of the duties conferred or imposed by those provisions is necessary because of danger to public health.