Limit,
You stop carrying your 20t after 12hrs due to Tow limit. Reduce it by 8.6t per hour after that. This would be why you only lift 37t of revenue out of SFO. Not much cargo there if you have have pax on board. This is why Glo stated the fuel burn per kg on these long sectors is the same for the 777 and the 380. Only the 380 carries 22t of revenue extra. Ek doesn't swap aircraft off routes to waste money. Same goes for the 748, LH may only load it the same as we do a 777, but it can carry its max ZFW a longer way.
The don.