Originally Posted by
musicmax
We're flying from the US to BRU via LHR. Will we have to go through Customs and/or Immigration checkpoints at Heathrow before boarding the flight to Brussels? Thanks.
As long as you are checked through to BRU from the U.S. then you won't need to clear UK Border formalities in London (in other words, traveling on a single ticket). If you are traveling on two separate tickets and have checked baggage, you would need to clear British formalities, go landside and check in again.