Apparently even if you add your passport details in the Swiss app, if it is within 72 hours of your flight to a non-Schengen country, you are not eligible to check in online, you have to check in at the airport.

Of course if I had simply received a pop-up or notification informing me that this was the issue, I would have felt fine about the situation. However instead you get a dreaded “Booking Not Found” message (which is…a bit scary?! It suggests you don’t have a ticket!). You can’t even FIND your reservation once the check-in window officially opens. This is despite the app sending me a reminder, and featuring a large red “Check-in now” button underneath my reservation.

I have flown many airlines globally, and have had status with a few different airlines over the years, and have never encountered the passport information as hidden as the Swiss app (there’s no alert, or section, or request to upload — it’s hidden in a submenu underneath the Profile section if you click on your profile).

Hoping this helps someone else in the future.