I’ve had a few instances in the last year of making changes to a booking that have required the issuing of a different e-ticket number. This has not been without its problems and has sometimes required phone calls to remind BA to get it done and, in one case, a rather nervous wait at an airport just before a flight while the checkin-agent got on the phone to sort it out. This seems to be a known issue, with the general advice being to let it take its course and, if nothing appears at T-72 hours, get on the phone.

I am curious therefore to know in what circumstances a new ticket might be required. For example:

-Upgrade with cash?
-Upgrade using Avios?
-Purchase of exit row seat?
-Upgrade at airport?
-Same day change?
-Change of date or time of return (either by airline or passenger)?
-Adding a return to an existing booking?

Would re-ticketing be required in some/all of these?