Nationality and Registration of Aircraft
The nationality link
An aircraft has the nationality of the State in which it is registered (Article 17), and it may not be validly registered in more than one State (Article 18). Registration may be transferred from one State to another only at the joint request of the two States concerned. Every aircraft engaged in international navigation must carry its nationality and registration marks and a certificate of registration (Articles 20 and 29).
The registration certificate
Under Article 21, each State supplies to any other State or to ICAO, on request, information about the registration and ownership of aircraft registered in that State. The certificate of registration itself is a document carried on board; it is not the same as the certificate of airworthiness (Annex 8) or the noise certificate.
Operators and the register
Registration is not the same as ownership or operator status. A State's register records the legal nationality link; the operator may be a lessee or a management company. Article 83 bis allows the State of Registry to transfer certain functions (such as licensing and airworthiness oversight) to the State of the Operator by agreement, notified to ICAO. This is a classic exam trap: the aircraft remains on the register of the State of Registry, but the State of the Operator exercises specific functions.
Joint registers
Some States operate joint or international registers (for example regional arrangements) under Article 77, which permits joint operating organisations. Candidates should not confuse these with flags of convenience, which are lawful but attract scrutiny.
Worked example
An aircraft registered in State A is leased to an operator in State B. If the question asks who is responsible for issuing the crew licences, the answer may be State B if an Article 83 bis agreement exists and has been notified; otherwise it is State A.