Thankyou that sounds simple enough, just do it the old fashion way (before online check ins existed!).
My main concern is trouble at MAD about the connecting flight to Australia. But it sounds like they’ll just not give me the 2nd boarding pass and tell me to get it in DFW at one of the transit desks?
Being the US, I’d have to collect and recheck any bags regardless, so it won’t really cause any issues there.
Assume for the return I can put the US passport into the booking and check in online and get both boarding passes. Although my Spanish resident visa is linked to my Australian passport, the EU doesn’t care which passport I use and doesn’t (currently) have an ETA/ESTA-like requirement for non-citizens.
