you probably have to speak to a human to get that changed

That’s restrictive. United lets you save 2 different passports on your profile.

Some airlines apps are more flexible for the lass common passport and visa combinations. Until fairly recently (the last couple of years) I had to manually check in for return flights to the US with almost all airlines. Now only occasionally do I need to do so. So eventually the apps might be updated if the check in desks start getting too many manual check-ins.
Andy

British Airways is the worst for this kind of thing. Years ago when I was on an L1 visa they couldn't comprehend someone who lived in the US (residence) who wasn't a USC or LPR. No checkin online and when I spoke to them they insisted that to be a resident in the US you must be an LPR - which I was not. They said they'd have to change my residence to UK to match my passport so they could add a visa to the system - insane.

I'm currently having fun with that as well with BA. I'm in Nigeria, flying back to Heathrow tomorrow, overnight Gatwick then on to Tampa Saturday. Using US passport details (as I have done for years), it now tells me I can't do online checkin because there is no ETA on file for the UK. So, I change my passport details to my UK one....and then it tells me I still can't checkin on line as I have no ESTA details on file for the US!! Bah. Airport check in desk it is then.

Hopefully they will adjust their website to factor all this in at some point in future.

Its mind boggling that an organization that specializes in transporting people across international borders all across the world hasn't got this figured out. Especially BA with the number of routes it has to the US.

Just get an ETA if you travel regularly.

But only if not a UK citizen. If they are, then a passport is needed, boarding can be refused without one even if they have an ETA. https://www.bbc.com/news/articles/c747vj1z0xwo

Yep. Admittedly it's only a very minor inconvenience having to stop by the desk (when travelling with no bags). It's just a bit annoying you now get penalised for having the two citizenships. As I say, I should think the carriers will revise their websites to accommodate it eventually

Some of us expats had to check in manually before the airlines allowed visas to be loaded into the passenger details. Maybe the airlines will get round to updating their systems to allow additional passports for dual citizens.
However, you should allow extra time at the airport for this step as there can be long queues for checking in.
Andy

oh boy! here we go again...

If someone has a valid ETA or visa linked to their non-British/Irish passport then they won’t be refused boarding. The woman in the article you linked to had neither which is why she was refused boarding.

It doesn't actually say if she had an ETA or not. I've now read about this happening to numerous people, including dual citizen kids travelling with non British parents (no mention of the parents being refused boarding too, so one assumes they had the requisite ETA). Some seem to have been stuck outside the UK for a while, which seems odd if they can just apply for an ETA? https://www.theguardian.com/politics...=share_btn_url

In all these cases the person "stuck" could simply apply for an ETA but they have been told they "can't" and so don't. The reality is the airlines don't know or care about the minutiae of British nationality law. They just know that they will receive a hefty fine for allowing someone to board a flight to the UK without either a British/Irish passport or a valid visa/ETA linked to their non-British/Irish passport.

I could do an A B test by entering a US passport for 1 and a UK with ETA for the other. . Both my mini tht have an ETA valid through 2027 in their US passports (applied and approved when the wording specified it was needed when you had no UK passport) and then when the wording was updated in early 2026 I ended up getting them both UK passports.

right now I have their UK passports saved on the airline app for the outbound and the US for the return trip from Europe. Now I need to double check if they need an ETA for Europe as well. Had to avoid visiting their EU country of Citizenship and go to a 3rd country as the NYC embassy has had no appointments for months to get a passport..