I remember reading somewhere else, CX claims TPE or PVG aren’t as profitable as others think, because a large portion of customers travelling on these routes are transit passengers, so if they split the revenue by distance, these short haul routes only count in for a small fraction of profit (i.e., if TPE-HKG-LHR in J is $3000 USD, TPE-HKG only counts for about $300). Based on the Forbes article in 2019, HKG-LHR is top 10 most profitable segment around the world, but this includes BA and VS as well. So I assume LHR, JFK would definitely be the most profitable segment.