Originally Posted by
Confus
If I were doing it, I’d add up the total fare plus YQ, then divide by the total GC mileage to get a rate per mile to build back into sector length. Thankfully I’m not doing it, because I doubt it’s particularly easy irl!
That's the way AF-KL do it for each fare segment. If you have different fares for different portions of the itinerary, each leg will be calculated pro rata of the (GC mileage of the) relevant fare segment. If you have a single through-fare, then it is a simple prorating on total GC mileage.