As I said in the prior thread, I'm still betting on this being a clerical error. I -- US citizen -- was once almost denied boarding of an international flight

As I said in the prior thread, I'm still betting on this being a clerical error. I -- US citizen -- was once almost denied boarding of an international flight because the airline's system had screwed up my passport information, and they thought I would need a visa to return to the US (and of course I didn't have a visa). I found this out at the airport. Luckily I was able to get it resolved in time by showing the airline agents my passport, and a supervisor was able to override or correct something to let me get a boarding pass, but relying on the kindness and competence of front-line airport staff is risky at best. I might just as easily have encountered someone who would tell me "The computer says no, and I can't do anything for you when the computer says no".