Well this shows why really Fraport should offer a special diploma course called “Layout of Frankfurt Airport”… Only candidates who get the highest grade at the end would be qualified to fly from FRA…😂😂😂😂

So as I understand it: it’s all to do with Schengen and non-Schengen on the one hand, and “clean” and “unclean” on the other. From some countries, pax arrive “clean” because (I guess) governments have agreed common standards. In particular, these “clean” countries include USA, UK (yes, even despite Brexit and the fact that the UK was never in Schengen, and also despite the fact that LHR offers no clean status to anyone arriving from anywhere except other UK airports), and I think also Canada.

This allows arrivals from “clean” countries non-Schengen countries arriving on B or Z gates to disembark into the boarding area of B or Z rather than the arrivals corridor. This means that, yes, you could in theory fly MAN-FRA-JFK with no security or passport check at all at FRA: no security because you were made “clean” in MAN and no passport because you don’t “enter” Schengen (you came from non-Schengen MAN and you’re going on to non-Schengen JFK, so you’re not formally leaving Schengen or entering Schengen- you’re purely in transit.)

All that is fine in theory. As mentioned elsewhere, the problem is the layout of the airport- the doors and corridors and separations of pax. So, for example, if at any stage the MAN-FRA-JFK pax is in the same space as a pax who has arrived from CAI (and I absolutely mean no offense to CAI or anyone who travels from there!!), the “clean” status is gone for all of them and those pax must all go through security before connecting onwards.

All of this is not helped by poor info- the “interactive map” on the Fraport website is terrible and I have yet to find a really good map or even a good explanation of connecting routes. Given that LHG arrive into and depart from such a wide variety of gates, a really detailed “arrival and transfer map” would be very useful.