Originally Posted by
layz
So when did SFO/LAX/JFK/etc trust LHR security?
They trust London City security when coming off the LCY-JFK flights - you could technically connect to a UA flight to SFO, say, in T7 and you would not have to re-screen. The US challenge - which is equally asinine to be sure - has to do with the desire to have pax clear customs at the point of entry into the US. When you pre-clear, out of City, Dublin/Shannon on some flights, or Canada, you do not have to go through security screening again.