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Travelling as a Dual British Citizen After 25 February 2026: Avoiding “Computer Says No”

From 25 February 2026, dual British citizens meet a new kind of border: the airline’s computer. If that system does not recognise you as British or clearly having right of abode for a UK‑bound flight, “computer says no” can mean you simply do not fly.

Step 1 – Booking the ticket: low‑risk stage

Booking is usually the least important part, document‑wise.

  • You can normally put in either your British passport or your other passport. The reservation is not welded to that document for life in the airline’s system.
  • You can appear in the booking as “British” or as your other nationality; nobody at the gate really cares what you clicked three weeks ago if, on the day, the airline records the right passport for the UK‑bound leg.

If you want to keep life simple, use your British passport details for the UK‑bound leg from the start. But if you booked with the other passport to get a fare, or to satisfy another country, it is not fatal – you can fix things later when the airline actually records your travel document at check‑in.

Step 2 – Online check‑in for the UK leg: where “computer says no” appears

This is where the new rules bite, because the airline’s online check‑in system now has to enforce “no permission, no travel”.

For a flight to the UK, that system tries to put you in one of two boxes:

  • Box A – British/Irish/right of abode: no ETA, but must show a British/Irish passport or a Certificate of Entitlement.
  • Box B – Everyone else: needs ETA or visa.

If you try to check in online using only your non‑British passport, the airline’s system treats you as Box B and starts demanding an ETA or visa. When you are actually British, that is how you end up in full “computer says no” territory.

As a dual British citizen you are not meant to solve this by applying for a UK ETA as a foreign visitor. The Home Office position is that you travel as British/Irish, or with right of abode, not as a tourist on an ETA.

So for the UK‑bound leg, the safest moves are:

  • Add or switch your travel document in the airline’s app or website to your British passport where it allows it.
  • If you travel on a Certificate of Entitlement, enter the details of that passport and certificate exactly as shown, and if the airline’s online system still sulks, abandon online check‑in for that segment and plan to use a staffed desk.

If the app simply will not let you change anything, do not waste hours arguing with it. Use it for other legs if you like, but accept that the UK‑bound flight will need a human to update the document details in the airline’s system at the airport.

Step 3 – Check‑in at the airport: where it actually gets decided

The real gatekeeper is the airline’s airport check‑in system for the UK‑bound flight. The staff are just doing what their screen tells them.

To be boarded to the UK, you must be able to hand over either:

  • A valid British (or Irish) passport, or
  • Your other passport with a Certificate of Entitlement to the Right of Abode stuck in it.

If all you show is a plain non‑British passport, the airline’s system is likely to say: “No ETA, no visa, no travel”, and the agent may not be allowed to override that just because you say “but I’m British really”.

What to actually do at the desk:

  • Hand over your British passport (or certificate‑bearing passport) first, even if the booking shows your other nationality. That lets the airline record you correctly in its system for the UK‑bound leg.
  • If the agent looks puzzled because the reservation has different details, something like this usually works:
    “I’m a dual national. I’m travelling to the UK as a British citizen, so this is the passport for this leg.”
  • If needed, ask them to update the passenger document record for the UK segment to match the British passport. Most airline systems allow this.

What not to rely on is turning up with only a foreign passport plus an old UK passport, birth certificate or naturalisation certificate and expecting airline IT to cope. Those documents prove your rights in law; they do not automatically satisfy the airline’s “no permission, no travel” checks.

Step 4 – Using two passports on one trip: the choreography

Many dual nationals still need the non‑British passport for the other country on the itinerary – for example, where they live now.

A simple pattern that works in most cases:

  • Leg to the UK
    • At airline check‑in: show the British passport (or certificate) so the airline’s system classifies you as British or right of abode, not as someone who needs an ETA.
    • At the other country’s border (exit/entry): show whichever passport that country requires from its own citizens or residents.
  • Leg back from the UK
    • Leaving the UK: you can show your British passport.
    • Entering your other country: show your non‑British passport if that is what that state expects from its nationals.

So in practice you might book with passport A, have the airline record passport B for the UK flight in its system at check‑in, and then use passport A again to satisfy your other country – as long as, for the UK‑bound leg, the airline’s records show you as British/Irish or right of abode.

Step 5 – Classic ways to get yourself stranded

A few patterns are likely to end in an argument at the desk – and another round of “computer says no”:

  • Treating the new rules as if nothing has changed, and rocking up for a UK flight with only your non‑British passport plus “evidence” that you are British. The airline’s system is not set up to adjudicate nationality from a bundle of paperwork at the counter.
  • Trying to dodge the problem by getting a UK ETA in your foreign identity, when in reality you are a British citizen. That is not what the scheme is for, and it may backfire inside airline and Home Office systems.
  • Letting your British passport expire and telling yourself you will sort it “when you next go to the UK”, then discovering at the airport that “next time” is today. From 25 February 2026, that is a boarding issue in the airline’s system, not just paperwork procrastination.

If you are a dual British citizen flying to the UK after 25 February 2026, the airline’s computer has the final say. Book however you like, but for the UK‑bound flight you must show your British passport (or a passport with a Certificate of Entitlement) so the airline can code you correctly. If you do not, do not be surprised when the computer says no

Migrant Law Partnership

Dual Citizenship-What you need to know

Postscript: who is most likely to be caught by the ETA rules?
If you are visiting the UK for up to 6 months and you do not normally need a visa, you will usually need an ETA from 25 February 2026. This includes, for example, people travelling on passports from EU and EEA countries (except Ireland), Switzerland, the United States, Canada, Australia, New Zealand, Japan, South Korea and many Gulf states such as Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the UAE. This is only a sample list – you should always check the official ETA national list, together with the visa‑nationals list, to see whether you fall into the “ETA, not visa” category.
In practice, the new rules are most likely to catch out British dual nationals who live long‑term in countries with large UK communities – for example Canada, Australia, New Zealand, the United States, South Africa and popular EU countries such as Spain, France, Germany, Portugal and Ireland – especially where children have never held a British passport and normally travel only on their “other” passport.