Originally Posted by
JohnAx
Good place to remind planners that add-ons really need to be round-trips since otherwise the surface segment created in the xONE would count in the 16-total. Worse, iirc the list of co-terminals for xONE purposes is limited, e.g. the several airports in the Los Angeles basin are not co-terminals.
IIRC, sadly, travel via co-terminals have been using one of the 16 segments for several years now(since "universal" e-ticketing).
i.e. -xLHR,LGW- uses one segment these days.