BCal/Sabena used to have a joint 747 service Brussels-Gatwick-Atlanta. I've flown the BRU-LGW leg. There must be shorter than that, though. I seriously doubt it was profitable.
Purely from a fuel cost point of view, a 747 would be optimised for a distance of about 5500km. Longer than that fuel burn per km rises very slightly due to ‘burning fuel to carry fuel’. Shorter than that, unit fuel burn increases strongly with decreasing sector length. But revenue yields are almost certainly going to affect the economics more than unit costs.
Last edited by The SSK; 22nd Sep 2011 at 12:44.