How can one identify if a passenger is domestic or international?

The identification of whether a passenger is on a domestic or international flight is most accurately done through the printed information on their ticket. Tickets generally contain specific details such as flight numbers, origins, and destinations, which clearly indicate whether the journey falls within national borders or crosses international ones. For example, a ticket for a flight from New York to Los Angeles would be considered domestic, while one from New York to London would be categorized as international.

While other options might seem plausible, they are less reliable. A passenger's nationality does not inherently determine the nature of their flight, as citizens may travel domestically or internationally. The seating arrangement may also have no correlation to the flight's categorization. Lastly, simply asking the passenger might yield inaccurate information, especially if they are unsure about flight specifics or misunderstand the question. Hence, the most definitive way to identify the nature of a passenger’s flight is through the details provided on their ticket.