What licences must pilots and flight crew have for international flights?

Under the 1944 Chicago Convention, all pilots and members of the operating crew engaged in international air navigation must hold certificates of competency and licences issued or rendered valid by the state in which the aircraft is registered.1

Additionally, if the aircraft carries radio transmitting apparatus, those specific devices may only be operated by flight crew members who possess a special licence for that purpose, also issued by the state of registry. These requirements ensure that all personnel operating aircraft across international borders meet standardized safety and regulatory qualifications established by the state responsible for the aircraft.1