Artikel XVIII

1. If either of the Contracting Parties considers it desirable to modify any provision of this Agreement or the Annex thereto, it may request consultation with the other Contracting Party; such consultation, which may be between the aeronautical authorities and which may be through discussion or by correspondence, shall begin within a period of sixty (60) days from the date of the request.
2. Any modification of this Agreement decided upon during the consultation referred to in paragraph 1 above shall be agreed upon by an exchange of diplomatic notes between the Contracting Parties and shall take effect on the date on which both Contracting Parties have informed each other in writing that the formalities constitutionally required in their respective countries have been complied with.
3. Any modification of the Annex to this Agreement decided upon during the consultation referred to in paragraph 1 above, shall be agreed upon in writing between the aeronautical authorities of both Contracting Parties and shall take effect on a date to be determined by agreement between the said authorities.