21.A.181 Duration and continued validity

(a)An airworthiness certificate shall be issued for an unlimited period of time. It shall remain valid subject to compliance with all the following conditions:

1.the aircraft continues to comply with the applicable type design and continued airworthiness requirements; and

2.the aircraft remaining on the same register; and

3.the type-certificate or restricted type-certificate under which it is issued not being previously invalidated under point 21.A.51;

4.the certificate has not been revoked by the competent authority under point 21.B.65, or surrendered by the certificate holder.

(b)Upon surrender or revocation, the certificate shall be returned to the competent authority of the Member State of registry.