Ok, so I purchased what I thought was a round trip ticket from BOS to SNN (Boston to Shannon) airport for a family of four. The Itinerary seemed strange, but the price was very good courtesy of Google Flights.

BOS to SNN; 10 days in Ireland!

SNN to LHR to DUB to BOS for the trip home.

When I visit the Aer Lingus web site it describes my tickets as such.

BOS to SNN (217 hr stopover) SNN to LHR. (Arriving in LHR at 9:50 AM)

Return Trip:

LHR (Departing at 11:50am) to DUB (4 hour stopover) DUB to BOS (Home)

It appears I bought a ticket to London with a long stopover in Ireland.

I am only in London for two hours. What is alarming is that it is not clear that my bags would be checked through LHR to BOS since that is the terminus.

Do I need to retrieve my bags and check in at LHR for the return trip to BOS in the two hour window I have at LHR?!?

Never mind the complexity of US customs since I know Shannon is a pre-clearance airport but LHR is not.

  • 1
    You're right that LHR isn't a preclearance airport, but Dublin is, so you'll be doing that during your four-hour stopover.
    – phoog
    Jan 12, 2017 at 14:54
  • 1
    Only slight related to the question, when you check in at SNN, ask if you can be sent directly to DUB. The worst that will happened is the Agent says no.
    – DTRT
    Jan 12, 2017 at 15:20

1 Answer 1


Do I need to retrieve my bags and check in at LHR for the return trip to BOS in the two hour window I have at LHR?!?

No. The baggage check system is totally independent of the fare construction on the ticket.

Instead, whether the baggage is checked-through or not is calculated from the arrangement of the flights on your PNR. In this case, you have a connection from SNN-LHR-DUB of two hours, between two carriers with an interline agreement; therefore your bags will be checked through from SNN to BOS via DUB and will not need to be collected and re-checked at LHR.

The Itinerary seemed strange, but the price was very good courtesy of Google Flights.

Google Flights is very good at finding low prices precisely because the underlying pricing algorithm from ITA Software divorces the fare construction from the way you have arranged your itinerary. Often it is now possible to find prices for journeys that were not even anticipated by the airline who published the fare.

  • 2
    Hmm, if the Aer Lingus website knows to display the booking as BOS-LHR outbound a LHR-BOS inbound parts, then apparently that division must have leaked beyond the raw fare construction phase, and the reservation backend contains not just a set of four segments that other systems must make sense of on their own, but also knows how they fit together as a round trip. Do you know positively that the system used for checking in baggage at Shannon doesn't use that same information when printing baggage tags? Jan 12, 2017 at 13:59
  • Wouldn't the traveler need to collect his bags at Dublin for preclearance? I've never flown through Dublin, only to and from it, so I don't know how that works.
    – phoog
    Jan 12, 2017 at 14:56
  • This Answer is very presumptive on how EI generates it bag tags. The default would be the current leg, of which there appear to be 3 or 4 (this is implementation dependent) so absent some fiddling, the bags would continue to the next destination, LHR. Unfortunately, the only one who can answer this question is EI. I won't downvote yet, but OP should be warned that this Answer is not definitive.
    – DTRT
    Jan 12, 2017 at 15:11
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    @phoog Thank you, I missed the DUB stop, although it does not change the final answer. There is no need to "collect" at DUB (or SNN) for preclearance; instead every connecting bag is photographed prior to loading and a photo of the bag is displayed to the pax who confirms that is his bag. If CBP are unhappy, they will pull the bag and inspect it. On BA 1, the bags are unloaded, photographed and reloaded onto the same plane while at SNN.
    – Calchas
    Jan 12, 2017 at 15:12
  • I am downvoting because this Answer makes a huge assumption on an Aer Lingus operational detail. Only Aer Lingus can answer this definitively, either an experienced Again on the phone, or at check-in.
    – DTRT
    Jan 13, 2017 at 15:11

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