Free upgrade. How to prove it is true?

Proof methods include upgrade confirmation form, boarding pass, official mail or SMS, etc.

1. Upgrade Confirmation Sheet: Airlines or upgrade service providers may provide passengers with upgrade confirmation sheets, including upgrade date, flight number, upgrade level and other information. The confirmation form shall be formally stamped or signed by the upgrade service provider or airline to ensure its authenticity and legality.

2. Boarding pass: Boarding pass can show the upgrade information and seat information of passengers, which is one of the important evidences to prove the authenticity of upgrade. At the boarding gate, the staff will indicate the upgrade and seat information on the boarding pass and affix the official seal of the airline.

3. Official mail or SMS: Some airlines or upgrade service providers may confirm the upgrade information to passengers by mail or SMS. These emails or text messages should be sent by authoritative people, including specific information about the upgrade and related precautions.

Free upgrade does not happen on every trip, and not every flight will provide this service. Therefore, if passengers need to upgrade, they should consult airlines or travel agencies before purchasing tickets to understand the specific upgrade policies and methods.