I'm flying to Dublin in a few weeks, not on a single ticket; I'm flying United SFO-LHR, and then three-ish hours later will be catching a flight LHR-DUB on BA. No checked baggage.

When I arrive at LHR, will I pass through customs and immigration, or will I not pass through customs until I arrive in Dublin?

(If it matters, I'm a US citizen, and not concerned per se about the transit - just wanting to know for planning purposes if we end up delayed since I'm flying on two separate tickets. I had to do the LHR round trip and then the Dublin flight separately since United doesn't fly LHR-DUB (or at least wouldn't show me any tickets) and London is my destination for half of the trip.)

  • 1
    In the vast majority of situations, airside transit is only available to customers travelling on a single ticket. The CTA also complicates things here (although DUB does make all passengers from the UK pass immigration there anyway)
    – CMaster
    Mar 21 at 16:12
  • 2
    Do you have checked baggage? If you have checked baggage, and there is not agreements between the two airlines about sharing baggage information (and code), you must pass immigration to go to baggage claim, then custom, then you must check-in the baggage again. Mar 21 at 16:20
  • 1
    You have separate tickets, and moreover UA and BA are in different alliances, so there's no chance that they'll check your baggage through.
    – xuq01
    Mar 21 at 16:32
  • 1
    @GiacomoCatenazzi and check-in before the relevant deadline (45 minutes before scheduled departure here). Also United arrives at T2 while BA departs from T5. IIRC there's quite a hike from T2 to the train platforms.
    – jcaron
    Mar 21 at 16:33
  • 1
    @CMaster I have done airside transit on separate tickets at LHR with a change of terminals involved, and absolutely no one cared. I just showed my first boarding pass at my first flight and my second boarding pass (obtained online, but there were also kiosks in the transfer area) at LHR. This maybe would not have worked if I had had checked luggage or if I was of a nationality that needed a visa to enter the UK, but the insistence on TSE that it is always impossible, or even impossible "in the vast majority of situations" is deeply overstated.
    – mlc
    Mar 21 at 23:31

1 Answer 1


On a self-transfer, with checked bags, from SFO using UA to DUB using BA your route will go like this:

  • Land at T2
  • Deplane
  • Go to passport control
  • Queue and go through passport control
  • Wait for bags
  • Go through customs
  • Go to the either the tube or train station
  • Go to Terminal 5
  • Go to departures
  • Queue and check-in before the departure deadline (45 minutes before scheduled departure)
  • Go through security
  • Go to your gate
  • Board before the gate closing time (I believe that's 20 minutes before departure, TBC)

While if your incoming flight is on time and there are no major issues at passport control or with the delivery of your bags 3 hours are plenty to do that (you probably have about 1 to 1.5 hours of buffer), a lot can go wrong:

  • Your incoming flight could be delayed
  • There could be a meltdown at passport control (and then it quickly goes to 2-3 hours waiting time)
  • There could be an issue with the delivery of your bags (I think that's a more common issue at T5 than T2, though)
  • It could take a while to go through security

And then your buffer evaporates, and your ticket is cancelled, and you have to buy a new one (at least minute prices), etc.

The good thing here is that there are plenty of flights from LHR to DUB, so finding a new flight shouldn't be an issue. Flights from LHR to DUB are quite more expensive than those from other London airports though.

  • Thanks - that's helpful. I probably can't change the Dublin flight due to timing, but what I'll do is make our less changeable plans for two days later and have our "free day" be the first one - that way if we do miss and have to reschedule for the next day, it doesn't mess up our plans!
    – Joe
    Mar 22 at 5:31

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .