So, we fly from the US to Barcelona (a chance to use "si us plau!), then a four hour layover before flying to Madrid, all on Iberia (though the US to Barcelona leg says "Operated by Iberia for Level Spain, whereas the Barcelona to Madrid leg just says "Iberia"). In Barcelona, will we be required to gather our checked luggage, exit the secure area through customs and immigration, then re-enter and go through domestic luggage check-in and security again? Maybe our bags will be shipped straight through, but we must go from an international are to a domestic area with the attendant immigration/security check again? Or maybe we never leave the secure area, but must go through immigration/customs? Or...what? FWIW, both arrival and departure in Barcelona are Terminal 1.
And, another oddity. When I later added reserved seating to the US to Barcelona leg (not gonna worry about assigned seating for the <1.5 hour flight from Barcelona to Madrid), the charge was in SEK! (Swedish Krona) What's that about?