I am hoping to make a round trip from Albany (ALB) to Stockholm (ARN).
At my target dates, one possibility is to go from: Albany to Newark (EWR) to Copenhagen (CPH) and then to Stockholm (ARN), and vice versa, using a combination of United Airlines and SAS. (So, United to get to Newark, then SAS to go from Newark to Stockholm, and vice versa.)
However, the layover at Copenhagen is short, one hour.
I am a US citizen but I don't have any experience traveling internationally, hence why I'm curious about layover times at other countries and if, other countries are intermediate stops, do we still have to go through some "immigration" or "customs" (I think that's what they're called)?
To be clear, I assume that when I arrive in Newark, I will walk over to some area for international flights, where people will then check my passport and such. The same for Stockholm.
My main question is if anything has to be checked during a stop where I'm not planning to leave the airport (as in Copenhagen)? I would do as much as I can to learn about the building of the airport so that I know exactly where to go from gate to gate, but if there's somewhere where I need to stand in line for an immigration or customs reason, that's what I'm worried about.
(I would also try and get these on one airline ticket, if possible ...)