Couldn't find quite the right answer to this question: I'm an EXP whose colleague is originating from a different city, but will be on the same flight to the final destination. I linked both of our PNRs and listed him for a companion upgrade. Our upgrades cleared right at T-100 mark- no problem there. However, I'm thinking about changing my flights - either by standing by or SDC the day of, while my colleague plans on taking the original flight. The question is- would his upgrade stay if I changed my flight? Anyone with similar experience? Thanks in advance!