I don't think that it's quite that simple. Yes, carrying extra fuel means you burn extra fuel to carry it. But refueling takes time - so for budget airlines in particular, which rely on fast turnarounds, it may be better to pay the extra cost of carrying the extra fuel, in order to save time, if that means that you can squeeze an extra flight in that day. Also, fuel costs aren't uniform - so it may be more economical to carry the extra fuel rather than pay the higher charge (I believe that this is called tankering). So airlines will work out on a case by case basis what is most profitable - in the scenario we're discussing sometimes this might be consolidating flights as you suggest, sometimes it might be tankering
Andrzej Kowalski ● 4d