Well, it's a tradeoff. If you make one really long flight, you need more fuel - and then you need more fuel to carry that fuel (though less). Basically you nee

Well, it's a tradeoff. If you make one really long flight, you need more fuel - and then you need more fuel to carry that fuel (though less). Basically you need an exponential amount of fuel for more range, not linear. (It works just the same as the rocket equation, though less drastic.) But landing and takeoff take kind of a fixed amount of fuel. So, for short trips, the fixed amount is more - so better to fly directly. But for really long trips, you're on the right side, the steep end of the exponential curve. Adding more range there takes a lot more fuel. So then it's smarter to put less fuel at start and make a refueling stop instead.