Why must aircraft on international flights display nationality and registration marks?

Under international air law, the requirement for aircraft to display nationality and registration marks is a fundamental principle established by the 1919 Paris Convention and maintained by the 1944 Chicago Convention.1

Displaying these marks is essential for several reasons:

• State Accountability: It ensures that every aircraft has a specific state that is answerable for it, preventing the existence of aircraft without a responsible governing authority.1
• Legal Jurisdiction: Nationality links the aircraft to the state of registry, allowing rights and duties to be channeled through that state. This includes the issuance of certificates of airworthiness, pilot licenses, and radio operating permits.1
• Regulatory Compliance: To benefit from the privileges conferred by the Chicago Convention, an aircraft must comply with international terms, which are enforced through the state of registry.1
• Operational Oversight: These marks facilitate the maintenance of required documentation, such as journey logbooks, and ensure that the aircraft and its crew meet the standards set by the state of registration while operating in or over the territory of other contracting states.1