I've got a question about TSA Precheck on an outbound international flight using a non-US passport.

I applied for Nexus about 9 years ago, and at the time, I only had one "active" citizenship: USA. I since learned that I had the right to claim a second nationality (an EU country) based on ancestry, and that I was legally considered to have had that citizenship since birth alongside my US citizenship. So though I've not acquired any new citizenships since birth, I've recently had the second one formally recognized and the second passport issued. I've considered going to a Nexus enrollment center and having them add my other passport to my profile, but after seeing several posts here about folks losing TSA Precheck after updating their nationality due to a known bug (sadly, in many cases, it is newly naturalized US citizens having this problem - not a very nice welcome), and knowing that I would never, ever enter the USA or Canada on anything other than the American passport, I've concluded that adding the other passport to my profile is going to cause more trouble than it's worth. So I won't do it unless asked.

Up until now, I would always check-in for outbound international flights to the EU with my US passport - which would cause a little mismatch issue if I tried using the automated passport gates on arrival in Schengen, but just going to the human passport inspector, it was never an issue. Obviously, I'd check in for return flight with US passport as well, and no issues using GE kiosks on arrival. But later this year, the EU will implement ETIAS, requiring non-EU citizens to be preauthorized to travel to the EU, and in the fine print, it specifically says that if you're a dual citizen with an EU passport, you're ineligible to use your other passport, you must be checked in on the EU passport (no ETIAS required). So that means I will no longer be able to check in for outbound flights with my US passport.

I understand checking in with a non-US passport on an outbound international flight is not a problem, as the requirement to present yourself as a US Citizen when leaving does not apply to airline staff. But what happens with TSA Precheck if I do that? I've got TSA Precheck as a US citizen enrolled in Nexus. My secure flight name, Nexus profile name, and name in both passports matches perfectly, as do the DOB and gender. In theory that should be sufficient to still get TSA Precheck even though I'd be checking in with a foreign passport (a nationality not eligible for GE, I should add). Will the system deny Precheck because I checked in with a non-US passport and thinks I'm not a citizen? Or will it say "secure flight and KTN info all matches" and still grant Precheck? I do have Clear, so I'm not totally screwed and can still get a shorter line if I can't get Precheck on outbound international flights...but just wondering what to expect and figure the experts here probably have a hint.

If I'm asked about new nationalities during Nexus renewal, I'll be honest about it, of course, even though in the most technical sense it is not a new nationality, but I don't believe I was even given the option to update nationality on the last renewal.

The PreCheck designation is issued based upon the KTN in the reservation, as long as the names on the reservation and the Trusted Traveler's match, not upon the passport that is used to check for the flight.