After 28 May 1999, the Convention shall be open to all States for signature at the Headquarters of the International Civil Aviation Organization in Montreal until it enters into force in accordance with paragraph 6 of this Article. This Convention shall similarly be open for signature by Regional Economic Integration Organisations. For the purpose of this Convention, a “ Regional Economic Integration Organisation ” means any organisation which is constituted by sovereign States of a given region which has competence in respect of certain matters governed by this Convention and has been duly authorized to sign and to ratify, accept, approve or accede to this Convention. A reference to a “ State Party ” or “ States Parties ” in this Convention, otherwise than in paragraph 2 of Article 1, paragraph 1 (b) of Article 3, paragraph (b) of Article 5, Articles 23, 33, 46 and paragraph (b) of Article 57, applies equally to a Regional Economic Integration Organisation. For the purpose of Article 24, the references to “ a majority of the States Parties ” and “ onethird of the States Parties ” shall not apply to a Regional Economic Integration Organisation. This Convention shall be subject to ratification by States and by Regional Economic Integration Organisations which have signed it. Any State or Regional Economic Integration Organisation which does not sign this Convention may accept, approve or accede to it at any time. Instruments of ratification, acceptance, approval or accession shall be deposited with the International Civil Aviation Organization, which is hereby designated the Depositary. This Convention shall enter into force on the sixtieth day following the date of deposit of the thirtieth instrument of ratification, acceptance, approval or accession with the Depositary between the States which have deposited such instrument.