Originally Posted by yubikey pressoooor

I'm a dual US-FR citizen, living in the US. When I go to Europe (France or anywhere else in the EU), I always have my US passport attached to the PNR because that's the most important of the two (can't return without it, and attached to Global Entry profile). I have never bothered trying to attach the EU passport on the outbound leg and the US passport on the return leg. I show my US passport to the airline on both ends, and only show my FR passport at the EU border control (both in and out).

Questions:

1. Nobody at the EU border has ever complained that my EU passport didn't show up on the reservation, automated kiosks or human agents. Is it because:
   1. the airlines don't transfer the inbound traveler info, or
   2. I am fully entitled to entry as a FR citizen regardless of paperwork lining up, so they don't care
2. Would it be different if I went to a non-EU country where I am not entitled to unconditional entry, perhaps one where US citizens have to pay a fee on arrival but FR citizens don't? For example, El Salvador.

In other words, are there any border controls where it matter that the passport on the PNR match what you present at the border?