Customs on EU flights

If you transit through LHR you do not cross the UK border and you do not go through passport control (nothing will change with Brexit). You will pass through passport control In Amsterdam as that is where you enter the Schengen zone.

If you transit via Frankfurt you will pass through passport control as that is where you enter the Schengen zone.

If you transit in Dublin “I think” you do not cross the Irish border so do not go through passport control just like LHR - but I’m not 100% sure. You will pass through passport control in Amsterdam as that is where you enter the Schengen zone.

You will go though customs in Amsterdam as that is where you will collect any checked luggage and may be subject to checks on the importation of goods into the EU.

As noted, at Heathrow on a through ticket you just transfer airside and do NOT go through Immigration or customs. You do have a security check between gates.

We flew from Seattle to Amsterdam on British Airlines last summer and the transfer at Heathrow was all in T5 and very easy.

Thank you for your comments this has really helped!

That said, It’s intersting to hear that LHR doesn’t require customs between flights as my in-laws had to go through customs and get their bags and recheck in while flying BA on the way to Barcelona on a through ticket. I’m wondering if something changed recently (this happened in October) or if they just had a very uninformed agent...

One clarification . . .customs , where and when you go through in Europe, is a non-issue. You simply walk through the door that is labeled “nothing to declare”. Your luggage will be checked through to your final destination no matter which option you choose, so not to worry. Passport control has been well-explained above.

Yes sorry and thank you for clarifying, I meant passport control. That is not the same. Thanks for catching my sloppy/lazy language!!

Ireland is not in the Schengen zone. It is in the Common Travel Area with the UK.

If your in-laws had to recover luggage at LHR then it must not have been checked through to the final destination. In which case they would need to cross the UK border to recover it at Heathrow's baggage claim before making their way to the second flight.

And you only go through the green nothing to declare channel at customs if you really have nothing to declare.

You seem concerned about customs? That is for declaring goods especially when returning to US., What I think you mean is passport control/ immigration and you would not enter the UK so just go through security. The UK is not in the Schengen Zone.
Dublin or Amsterdam are in the Schengen Zone so you would go through passport control in the first one you pass through.
I have changed planes at LHR many times, usually changing terminals and they have it all worked out so transfers go smoothly. They even a place on the airport website to enter your two flights and it gives clear and detailed instructions for your transfer. I have transferred to a international flight home with only 60 minutes.
I do not understand why Brexit is a factor.

Yes I was incorrect in calling it customs, I already commented on that above. I was worried about having to do the whole immigration/passport check as that has been a hellish experience for us in the past at LHR and any changes to immigration laws can make things more confusing/take longer, hence the concern with Brexit making things more difficult.

Thank you for letting me know about that site, I will search for it and try to find info on specific flights we are considering. I’ll also look into the schengen country rules so I know what to expect there.

Thanks again everyone!

To reiterate - Ireland is NOT in Schengen.

Thanks, yes I see it’s not in the Schengen Zone. Wikipedia has a full list I am consulting to understand times for connections. (I’m sure there’s a more official list but Wikipedia works lol)

Also, to the person who said 60 minutes is a doable connections, thank you for that. That helped me feel good about some of our options with 90-100 minute layovers in LHR.

I would not book anything less than a 3 hour connection despite individuals who have done well with less. Too many things can go sideways.

I would probably choose Dublin as it is a smaller airport than Heathrow and Frankfurt which should make the transfer easier. And they have US border preclearance.

Frankfurt IS a large airport, but well-organized. We transferred there on our way to Vienna, no problems, no delays.

The customs/immigration confusion is common; I've heard cabin crews fall into it. Be prepared, however, to produce your passport for other reasons. Your cabin luggage, for instance will go through security clearance in whatever gateway you enter and you will likely have to prove your identity then to get on the next flight. Brexit, however it does or does not happen, can't make Heathrow any more arduous than it already is. Anything under two hours for transit there is already risky, especially if moving to a different terminal for departure. But wait: Heathrow is big because it is a useful gateway and, aside from occasionally indistinct traffic signs, efficient. To expand on another point, if you return through Dublin, you will go through US immigration security in that airport on the flight home.

Your inlaws were given bad information.

For a transfer at LHR, go to http://www.heathrowairport.com/flight-connections, plug in your flight information and it will give you step by step instructions.

If you are on one ticket.......your checked luggage should be checked through to your final destination where you will go through customs.

For Heathrow and Dublin, you do not go through immigration there. Just security.

For Frankfurt, you will enter Schengen there and to through immigration there. That means your flight from Frankfurt is like a domestic flight. You just walk off the plane and collect your luggage.

Where you transfer really depends on what airline you'll be flying.

I agree that Frankfurt is well-organized, and I usually don't mind a transfer there. But it is a large airport.

But I'm not a fan of Heathrow, not only because it's large. But also since it operates at 100% capacity small delays or disturbances can cause pretty big trouble.