Flight transfer

Knowing your exact scheduling would be helpful. If is possible that you would clear immigrations (different from customs) in Ireland and shift to a domestic flight. You generally go through immigrations in the first country you land and customs at the end.

Frank, it is a United flight that lands in Dublin at 10:25. I depart on another United plane (which is operated by Aer Lingus - I guess in partnership)3 hours 45 minutes later. Since Ireland and England are separate countries, I wasn't sure what the process would be. None of those flights would end up being domestic. Thanks!!

Assume you are going to London? The second leg is consider a domestic flight in Europe. Probably immigrations in Dublin and customs in England when you have access to your checked luggage.

Sorry, I forgot to put the second leg. Not going to London - heading to Manchester. I hadn't thought about it being considered domestic, but they both are EU countries. Thanks!

Thanks for your help, Frank!

Immigration and customs for carryons will be in Dublin. Customs for any through-checked bags will be in Manchester.

Neither Ireland nor the UK are in Schengen, and I don't think they have a common "visa" zone like Schengen. If you leave the international area in Dublin airport, you would have to go through immigration there and in Manchester. If they have an international transit quarantine area, like LHR, you would stay there and avoid immigration and customs.

However, they are both in the EU, which is a free transport of good zone, so there shouldn't be any customs between them. If your checked bags are checked through to Manchester, you would get them there and go through customs with them. In 13 trips into Europe, customs has always been a walk-through.

The answer is probably complicated to be dependent on a number of things. All other things being equal and the fact that you are on a US flagged carrier for both legs, very likely means that your time in Dublin will be treated as if you are in transit. This means you will get off the plane, stay in a secure international area and proceed to your gate without encountering immigration or customs, encountering those requirements in Manchester.

However, Ireland and the UK do have a Common Travel Zone agreement that eliminates most checks between borders. This really only applies to UK and Irish Citizens, but everyone else gets caught up in the process. Enforcement and checks can be hit or miss, I know on flying beyween the UK and Ireland, as a non-citizen, I did have to go through Irish immigration, and at least once, I had to go through UK immigration. It does depend whether the flight is classed as domestic or international, and even on domestic flights non UK and Irish citizens may still have to go through immigration, or at least a passport check. Since the Dublin-Manchester leg is by United, it may still be an international flight.

There are absolutely no routine immigration checks when travelling inside the CTA by the UK Border Agency with the sole exception of visa nationals. So if the first landing point is Dublin, processing is done by the Irish authorities. This does mean no one who needs to activate any specialist kind of visa should enter the UK via the Republic of Ireland.