A flight ticket number (often called an e-ticket number) is a unique 13-digit numeric string that serves as the official proof of purchase and "contract of carriage" between you and the airline. It is distinct from your 6-character alphanumeric PNR (Passenger Name Record) or "Booking Reference." The first three digits of the ticket number represent the airline’s specific IATA numeric code; for example, American Airlines tickets start with "001," United with "016," and Delta with "006." The remaining ten digits are the unique identifier for your specific journey. On your receipt or mobile boarding pass, it might be labeled as "ETKT," "Ticket #," or "Document Number." You can usually find it near the bottom of your confirmation email or under the "Passenger Details" section of your e-ticket PDF. It is a vital piece of information because, while the PNR only links to your reservation, the ticket number proves that the flight has actually been paid for and issued. If you have a PNR but no 13-digit ticket number, your booking might not be fully confirmed, and you could be denied boarding at the airport.