Originally Posted by
Dannyboy39
I still don’t understand why whenever you are connecting onto another international flight (or going to a domestic from international), you have to clear security again at the connecting airport.
I would understand if some countries would be classed as high risk, but going from UK-USA and vice versa, is the USA suggesting that the security methods are not good enough? Surely there’s enough cooperation to trust each other’s protocols.
But "whenever" is not universally true. Some countries will accept other countries' security screening. As I said above, there are intra-Schengen arrangements that mean that security screening in any Schengenland country is usually considered good enough for connection in any other Schengenland country. And within the EU subset of Schengenland countries, this is a big part of what makes all of these international flights feel like domestic flights: no immigration or customs controls, and no repeat security screening if connecting.
Similarly, the Netherlands (and quite a few other EU countries) accept UK security screening. if you fly on BA from London to Amsterdam, you will disembark straight into the departure gate area where you mix with passengers flying from Amsterdam to London without having to clear security again, and you can fly straight back to London without clearing immigration, customs or security at Amsterdam.
If you fly UK-US and then connect to a US domestic flight, you have to be security screened again for this reason if no other: The stream takes you through areas where you have contact with checked baggage. That automatically means that you must be security screened again before any onward flight.
If you fly US-UK and then connect to a UK domestic flight,
AFAIK there are no special arrangements at any UK airport for segregating "safe" international arrivals from non-safe arrivals, so everyone must be treated as non-safe and require security screening at the UK transfer airport, as
DaveReidUK says. This would apply even if the UK didn't have a rule that (AIUI) trusts no other country's security screening.