The stub is irrelevant. Itu2019s just a record for your personal use. All airlines use one of two u201chubsu201d - computerized centers that process all ticketing and revenue related transactions. These companies are Amadeus and Sabre. Southwest has their own system, but last I head they were dissolving it and moving to Amadeus. These companies assign each passenger a PNR number, and while those numbers get re-used over the years, they are unique in databases in that they are paired with a date and time down to the nanosecond as a key. So, these records, by law, are retained for a number of years. I think 10 active archive and then they can go to inactive archive for another IDK how long. A long time. Anyway, these computer systems begin tracking a passenger as soon as they hit the airport, and paired with the DHS and airline verifications of identity at airports, they work as an admissible record of evidence in a court of law. These computer records track every layover, plane change, and missed flight. If you fly from LA to NY and layover in Nashville, and then jump off the plane and buy another ticket cash with a fake ID in Nashville, they will still know your original ID did not continue the flight. Cameras do the rest of the work. So these computer records can be easily requested from these companies and typically would be handed over cooperatively vs requiring a warrant, as these companies have no benefit or desire to protect your privacy if you are suspected of some kind of criminal activity.