The "passenger number" on a ticket can refer to two different things depending on the airline's system: either the sequence number or the Frequent Flyer Number. On a boarding pass, you will often see a "SEQ" number (e.g., SEQ 024); this indicates the order in which you checked in for that specific flight. Passenger 001 was the first to check in. This number is used by gate agents to manage standby lists and boarding priorities. However, if the "passenger number" is a long, permanent alphanumeric string, it is likely your Record Locator (PNR) or your unique Frequent Flyer ID. In the context of "Secure Flight" data for 2026, your ticket may also list a "Known Traveler Number" (KTN) if you have TSA PreCheck. It is a peer-to-peer security essential to never share a photo of your boarding pass online, as the barcodes and passenger numbers contain sensitive data that can be used to access your full itinerary, home address, and payment details through the airline's "Manage Booking" portal.