Why does an aircraft flying internationally need a certificate of airworthiness?

Under the 1944 Chicago Convention, an aircraft engaged in international navigation must carry a certificate of airworthiness to ensure it complies with the safety and regulatory standards established by the state in which it is registered.1

This requirement, outlined in Article 31 of the convention, serves as a fundamental mechanism of air law to guarantee that every aircraft operating internationally is held accountable to a specific state. By requiring this certificate—which must be issued or rendered valid by the state of registry—the convention ensures that all aircraft benefit from the privileges of international air navigation while maintaining consistent safety oversight. Along with other mandatory documentation, such as certificates of competency for the crew and registration marks, the certificate of airworthiness is essential for verifying that the aircraft meets the legal and technical criteria necessary to operate safely across international borders.1