[jonah]

We transited through LHR yesterday. Still had to go through security - not sure why since we stayed on the air side.

Anyway, signage required us to empty our refillable water bottles. Odd. Thankfully we eventually found a refill station.

The scanners flagged a still sealed can of ginger ale left over from our incoming flight. It was "fine" but she still swabbed it. Shrug.

[al_borland]

If you come in from a country that doesn’t fall under the TSA, you have to clear TSA before getting on a flight that does.

The worst I had was in India, flying to the US. Not only was there the normal airport security (despite having come in on a connecting flight from within India), but when I got to the gate (with only minutes to spare), there was a whole TSA check at the gate itself. Bags x-rayed (again), metal detectors (again), guy with a wand (again), the whole deal. Just getting to the gate, I had to show my papers to at least 6 people; every time I turned down a new hallway. That was my far my worst airport experience.

[jakub_g]

Flying with connections mostly within Schengen, or EU<>US via CDG, I never had to clear security again at layover, but I recently learnt this is rather an exception, and apparently it's a very common thing in most airports to have to clear security again.

LHR is actually notorious for this; you don't have to clear security again at LHR only when the connection is domestic.

In many other airports it's the same when e.g. you switch a terminal. Best to check for a particular airport what are the rules before booking.

[stevage]

It's super frustrating losing the contents of your water bottle and then having nowhere at all that you can refill it.

[jacobp100]

I think all UK airports have easy to find water bottle refill stations

[stephen_g]

Pretty common to have to re-clear security at large airports if you've come from another country, I've had to do it every time when transiting through Dubai for instance.