A U.S. citizen flying ORD-OSL-ARN (both legs booked together as one flight on Norwegian): would he go through passport control at both OSL and ARN, or just at ARN?

I would guess at the entry point to EUrope,which would be OSL. Anything after that you are covered by the Schevening treaty.

As @elbanditoroso has said, the Port of Entry to Europe will be Oslo, so that’s where his documents will be checked, I would presume. After that there should be no check at Stockholm.

But this is presumption on both our parts, because this is how things normally work. Why doesn’t he check with the airline to be sure? (And with the vagaries of scheduling flights these days, I wouldn’t count on a 1-hour layover at the end of a transatlantic flight in any case.)

It depends whether he switches flights or stays on board he same aircraft and the connecting flight is not flown as a regional flight.

In this case it seems clear he switches flights. Since both Sweden and Norway are members of the Schengen treaties on free border movement, there will be no check between Sweden and Norway. Therefore Oslo is point of entry and he clears passport control upon entry in Oslo.

It shouldn’t be a problem, though. Oslo isn’t a very busy airport and in case the connection is thight he should point that out to ground staff and make sure he gets through the fast lane. Passport clearance should not take more than 10 minutes.

It is not like travelling to Saudi Arabia where everybody scrambles to be the first in line and still may have to wait for two hours.

Thank you—wow, passport control at OSL is that fast?! That seems amazing!

Actually…
The information I gave you yesterday, I got from a colleague, but is not (fully) correct.

She was right with the passport however there seems to be a serious issue with this airport still: they make you collect your baggage and then check in again.

This may take some time and has actually created problems on connections to people.

Please verify with your airline. It shouldn’t necessarily be a problem and this flight combo may likely still be your best choice to get to Stockholm.

Thank you! Luckily I don’t believe he has ever checked a bag (believer in light travel) so we should assume no bag to collect. But I will tell him to contact the airline and/or check the history of the transatlantic leg to see about that flight’s history of on time performance.

OSL is very quick with the passports, I am norwegian, and when re-entering the country I dont factor in the check in my time measures.

There is one issue thou, on some streches OSL requires you to collect and re-check your luggage when switching from one international plane to another.