Originally Posted by
DaveReidUK
Not necessarily.
On a two-leg journey, a greater proportion of the overall flight time will be spent at lower altitude, in the climb and descent x 2, where the solar radiation effect is less. I think we need to see the sums.
On a two leg journey, you will probably also be flying at a higher cost index, thus faster, as conserving fuel is less of an issue. Next to this ULH is more likely to go over the (north) pole, which has more ionic radiation.