This has been somewhat discussed in a couple of other threads, but I didn't see exactly how airlines and countries are handling APIS information in the case of a dual national traveling between the two countries of their citizenships. The concern is that traveling from Country "A" (which does NOT accept dual nationality), checking in with the airline with country "B"'s passport (the destination country, which doesn't care about dual nationality), the airline might share the check-in data with the departure country via APIS. Concrete example: Spanish-US dual national. Spain does not accept this dual nationality. The US doesn't care. Check in with an EU airline for a flight Spain-US. The "easy" thing to do (so that the airline has no doubt that the passenger has landing rights in the US, without a visa or ESTA) would be to check in with the US passport. (And then show the Spanish passport at Spain's exit passport control checkpoint). But, will the airline send APIS data to Spain (the country from which the flight departs)? .. in which case there's some risk that Spain (which doesn't accept dual nationality) might get a bit upset (if it realized that this one physical person has two different passport identities).

On the other hand, the passenger could check in for the flight from Spain to the US using their Spanish passport, and then show the airline check-in staff (surely they'd be unable to use the kiosks and online check-in) their US passport, so that the airline would be satisfied about landing rights. IFF the airline sent APIS data to Spain, then Spain would just see a Spanish citizen flying out of Spain - no problem. The US would get APIS data about an arriving Spanish citizen, which might result in a question at US immigration, but as the US doesn't object to this, it shouldn't be a big deal. (It might, however, prevent using the self-service kiosks and Global Entry, which would be an unwelcome pain).

So, does the ever-more-common APIS (all the countries these days want all the information they can gobble, from everywhere, as early as possible) create any new complexities for dual nationals traveling between a country of their nationality which does not accept dual nationality, and the other country of their nationality?

What is the most convenient (still able to use automated check-in and especially immigration/ US Global Entry kiosks) strategy of which passport to use when, while ensuring that the country of citizenship which does not accept dual nationality doesn't get upset?


  • 2
    Does this answer your question? I have two passports/nationalities. How do I use them when I travel? The safest option is to fly by way of a third country, using separate tickets.
    – phoog
    Sep 1, 2021 at 14:22
  • 1
    The US APIS Implementation Guide is here. According to that, for the example in your second paragraph the US would get an APIS record with the Spanish passport 72 hours before the flight and then get an update adding the US passport at check-in time. If Spain gets a copy of all APIS messages they'll see the US and Spanish passports in the same record, which would make the issue even more obvious.
    – user38879
    Sep 1, 2021 at 16:26
  • Hi @phoog, I had read that and its linked thread before I posted my question.
    – Jay Libove
    Sep 1, 2021 at 20:14
  • @dennis But that's exactly my question - whether the originating-in-Spain airline sends APIS data also to Spain, or only to the destination country US.
    – Jay Libove
    Sep 1, 2021 at 20:14
  • @JayLibove, As I mentioned I was only addressing the second paragraph, which assumes that Spain gets APIS data ("IFF ...") but might not learn about a US passport used at check-in. That's unlikely.
    – user38879
    Sep 1, 2021 at 22:27

1 Answer 1


I don't think you will be allowed to board a flight to the US with your Spanish passport on file and without ESTA or visa: the info will be sent to CBP and they will return "DON'T BOARD". The airline will have to update your API info before boarding with your US passport for you to be cleared to board. They can't just see your US passport and let you board (as would happen for other countries which don't use API-like procedures or countries which only receive it as information rather than to trigger a board/don't board response).

In EU countries where you are protected by GDPR, you should be able to get the information from the airline on how they will handle your data and who they will share it with. However I fear it might be a somewhat vague "authorities which require it" which doesn't state whether it's the origin or destination country or both. In many cases (especially countries without exit checks such as the UK or the US), they will share it with the departing country (though I'm unsure as to what exact data they share).

If you really want to be sure they don't find out, your only option is to travel via a third country.

Note that there are a lot of exceptions which allow dual citizenship for Spanish citizens (depending on how you got each citizenship). You might be worrying unnecessarily. And even if in your case it's actually not allowed, it might be interesting to check what the penalties could be and especially if it's actually enforced. Many countries which in theory don't accept dual citizenship don't actually enforce it.

  • Thanks @jcaron. There's no doubt that, officially, my situation "isn't allowed". I'm relatively confident that it's unlikely for Spain to actually make hash of it, but if there is a workable balanced solution of course why take unnecessary chances? Good point about APIS and an inability to check-in. Giving the departing-from-Spain airline the US passport clearly is what's needed about that.
    – Jay Libove
    Sep 1, 2021 at 20:15
  • @jcaron "And even if in your case it's actually not allowed, it might be interesting to check what the penalties could be and especially if it's actually enforced." penalty is likely losing citizenship? Not something that would be interesting to test out... as if it is enforced, you lose EU citizenship.
    – kiradotee
    Sep 20, 2021 at 20:59

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .