Heathrow does not, in fact, offer US pre-clearance. It is, however offered at both Dublin and Shannon International Airports in Ireland. 'The term “immigration” is sometimes used, but the proper term is “Customs.”' Erm, no. The two are mutually exclusive.

As of early 2026, London Heathrow (LHR) does not have a fully operational US Preclearance facility, although it has been a topic of high-level government negotiation for nearly a decade. US Preclearance allows passengers to clear US Customs and Border Protection (CBP) at the departure airport, meaning they arrive in the US as "domestic" passengers and can skip the long immigration lines. While Heathrow was identified as a priority site for expansion, the logistical challenges of retrofitting Terminals 2, 3, 4, and 5 with secure "sterile" zones for US officers have caused significant delays. If you are flying to the US from the UK and want the Preclearance experience, you currently have to fly from Dublin (DUB) or Shannon (SNN) in Ireland. However, rumors persist that a dedicated "Preclearance Wing" may be integrated into future Heathrow terminal expansions. For now, if you are departing from Heathrow, you will still undergo the traditional process: you board your flight as usual and clear US immigration upon arrival at your first point of entry in the United States, such as JFK, LAX, or Chicago O'Hare.