Article 3 For the purpose of determining the obligations of Contracting States under this Convention, birth on a ship or in an aircraft shall be deemed to have taken place in the territory of the State whose flag the ship flies or in the territory of the State in which the aircraft is registered, as the case may be. Article 4 1. A Contracting State shall grant its nationality to a person, not born in the territory of a Contracting State, who would otherwise be stateless, if the nationality of one of his parents at the time of the person's birth was that of that State. If his parents did not possess the same nationality at the time of his birth, the question whether the nationality of the person concerned should follow that of the father or that of the mother shall be determined by the national law of such Contracting State. Nationality granted in accordance with the provisions of this paragraph shall be granted: (a) At birth, by operation of law, or (b) Upon an application being lodged with the appropriate authority, by or on behalf of the person concerned, in the manner prescribed by the national law. Subject to the provisions of paragraph 2 of this article, no such application may be rejected. 2. A Contracting State may make the grant of its nationality in accordance with the provisions of paragraph I of this article subject to one or more of the following conditions: (a) That the application is lodged before the applicant reaches an age, being not less than twenty-three years, fixed by the Contracting State; (b) That the person concerned has habitually resided in the territory of the Contracting State for such period immediately preceding the lodging of the application, not exceeding three years, as may be fixed by that State; (c) That the person concerned has not been convicted of an offence against national security; (d) That the person concerned has always been stateless. 80