Originally Posted by azzurro

I disagree. I have flown 1M+ miles with UA and it only happened once, but it did happen...RT: DEN-ATL via connecting cities. On the return leg ATL-IAD-DEN I checked in via app in ATL, scanned my bp (heard the normal beep) and took my seat. Landed in IAD and noticed I was no longer on upgrade list. Checked with gate agent and they said my ticket was cancelled for not boarding the flight I just landed on!!! (But I was on it and they didn't notice when they did the final count that they had 1 more passenger than the manifest showed!) The IAD -DEN bp was no longer in my app and I had no record of ever being on that flight because, also for the only time ever, that morning I tossed my printed itinerary because I had never, ever needed it up to that point so surely I wouldn't need it that day either. What timing and coincidence. In the end they reinstated the cancelled ticket at full fare and put me on standby. I was lucky enough to get a bp and get home, but not in my exit row 21 window seat and learned that even though it only happened once over thousands of flights - it does happen, it was THEIR fault (I did not mess with any app changes nor was there MX or WX going on) and I will always keep written proof. I even go to kiosks and reprint bp's at every flight so I have proof. Fool me once, shame on you. Fool me twice...isn't gonna happen.

So for those who say this displaced passenger must have mistakenly cancelled her flight, while it could have happened it is also very fair to call poppycock as systems do make mistakes that are not immediately easy to discern what or where it went wrong.