Originally Posted by
BertieBadger
I think this is saying that some fares allow it to be booked as a NCL-LHR in CE, and a LHR-DFW in WTP and the two fares/trips effectively joined together and that once that is done the end result is a NCL-LHR-DFW ticket that costs less than booking it as a single "through fare", and as such BA.com offers up the cheaper version with the CE ticket?
Yes, that's right, though I wouldn't regard myself as a ticketing expert, merely someone who consumes rather a lot of them.
End-on-end ticketing is where you have a fare component for NCL-LHR and a separate fare component for LHR-DFW, and the fare rules of both components allow them to be connected to provide a single NCL-LHR-DFW. There would still be two fare basis, but one PNR and from the outside the join is invisible. Through fares would be tickets which are constructed right from the start as NCL-DFW tickets, and may well have a rule in saying you have to go via LHR (for example). So from the outside it's identical to the end-on ticket but it could cost more, or less, and have different fare rules.
Sometimes end-on-end ticketing is inevitable, no airline is going to file, maintain and manage every single flight combination, but it does explain why sometimes it cheaper to go from NCL as opposed to EDI or GLA, even though all three airports are quite close together (by my rural standards).