Originally Posted by AlanB

rdorman,

The bar code does not change, not matter what changes you make. The only way to get a different bar code is to cancel outright and start over.

The one thing that I'm not sure of, although presumably the CA agent can also scan the QR Code, is how the agent will know you did an upgrade and to grant you access to the lounge, since the paperwork would still say BC on it. Even if they can't scan the QR code, they should still be able to look up the reservation, but that is of course more work for them which some may not like.

It's also going to be an interesting exercise for the FC crew in the car, as many like to check to make sure that you actually belong in that car and they will have no way to know that you processed an upgrade. Only the conductor will know that; so I would not be surprised to see a slight increase in people being kicked out of FC because they have the wrong ticket as it were.