Can i clear US immigration in Heathrow or do i have to wait til i land in Dulles?

Question

why answer when you don't know. You can clear in Ireland from two airports bibs.....

Answer 1

The US Immigration and customs must be cleared on US soil for all flights originatinbg from outside the North American continent. You can clear the US Immigration & customs at some originating airports in Canada and Mexico but not in Heathrow, London.

Hope this helps!

Answer 2

You must clear in the US.