I'm sure this has been discussed before but I'd appreciate it if you (oneworld4u) could clarify the co-terminal situation a bit more. I understand surface segments, but this LGW/LHR thing still confuses me based on past experience.

In September 2006 my paper ticketed DONE4 said GIB-LON-DXB-...-TYO-...-NYC-...-SFO-LON-GIB. It was a 20 segment ticket and while I arrived and left from the same airport in the first 3 instances, my last flights were SFO-LHR, LGW-GIB -- I would have tipped over to 21 if it hadn't said LON. Is it now explicit that city designations aren't allowed?