A noise certification shall remain valid on condition that -
(a) the holder thereof complies with the applicable type-design, environmental protection and continuing airworthiness requirements;
(b) the aircraft for which the certificate is issued retains the same registration marks;
(c) the type-certificate or restricted type-certificate under which it is issued has not been previously invalidated under Regulation 21.02.11; and
(d) the certificate has not been suspended, or cancelled in terms of Part 185 or surrendered.