Originally Posted by
televisor
I believe the US and Canada are considered sterile, so is there any reason a EU exit would affect the UK being considered sterile? (I'm not 100% sure about the US/Canada though, correct me if I'm wrong.)
And the UK considers any foreign country unsafe, it's not just ZRH. That's one good reason to avoid transiting the UK IMHO.
US/Canada are NOT considered sterile.
What some Canadian airports have is what's called a transborder region - you go through US customs at the Canadian airport and enter a "sterile US" area, you then land as a domestic flight in the US. But there's no sterile combined US/Canada area (e.g. if you fly from the US to Canada, you always clear customs before flying onwards)