I’m flying into IAH from LHR on a BA flight, looking to then fly to Cancun CUN on a United Airlines flight, how long should I allow for the transfer, and upon arrival, do I need to collect luggage, go through US immigration to then check in for the UA flight to Cancun, or is there an airside process to avoid this? thank you.

  • Are both flights on the same ticket or bought separately?
    – jcaron
    Oct 10, 2023 at 16:48
  • 1
    you will need to clear customs and exit the terminal and re-enter into the departures section for the United Desk for check in. The airport is under huge construction at the moment, I would give atleast 2 hours for transfer.
    – AussieJoe
    Oct 10, 2023 at 17:55

1 Answer 1


Given the combination of airlines, I believe you are considering flights booked separately.

While any transit via the US, whether on the same ticket or on separate tickets, will require you to go through passport control, retrieve your bags, and go through customs, there are still some important differences:

  • On a single ticket your bags would already be tagged to your final destination, and you would drop your bags just after customs, which takes seconds. On separate tickets you have to haul your luggage to the departures area, queue at the check-in/bag drop for United, and drop your bags before you can move on to security and on to your gate.
  • You will have to drop your bags before the check-in deadline for your second flight (60 minutes before departure). If you don’t, you will be considered a no show, and your ticket is very likely to be cancelled, including further segments on the same ticket. You would then need to buy a new ticket at last minute prices, usually a lot more expensive. If the next (available/affordable) flight is the next day, hotel, meals and transfers are on you. On a single ticket if you miss your connection the airline would rebook you and pay for all that.

Even if your incoming flight is on time, 2 hours is IMHO the bare minimum just to make it, with very little margin. Maybe a bit less if you are at the front of the plane and go through the quicker queues at passport control, possibly quite a bit more if you are a first-time visitor with a visa.

I would not recommend doing this without at least 4 hours, possibly more. I personally wouldn’t do it without staying overnight, unless I’m sure I can get another flight quickly and at a cheap price, even at the last minute.

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