Originally Posted by qasr
A circle trip, at least fare wise, is usually 3 one way fares. E.g. in your example A: SEA-LHR, LHR-IAD & IAD-SEA would be 3 (very expensive) one ways.
I don't believe that's true (at least that not what we learned in MR 101). The fare on each leg of a circle trips is 1/2 the round-trip fare.
Originally Posted by mymiles2go
And can any trip with more than two stops be a circle trip? Does it simply have to end at the same location to qualify as a circle trip? Failing that, is it an openjaw?
Pretty much. There is no difference between a circle trip and a trip with a stopover.