In a circle trip, you fly to two different cities before returning to the originating city, and each leg has its own fare, so there are no bonus/free stopovers.

For example:

Leg 1 ATL-LAX K fare, $200
Leg 2 LAX-PDX (xSLC) M fare, $150
Leg 3 PDX-ATL Q fare, $275

Total fare: $625. No free stopovers. You complete a circle.

Now, if the fares ATL-PDX allowed stopovers in LAX, you could do the identical trip above and build in a stopover in LAX, in which case it would seem like a circle trip but it would really be, for the purposes of fare nomenclature, a roundtrip ATL-PDX with a stopover in LAX on the way out.

So, a circle trip really refers to how the fare is constructed. If you're visiting two different cities before returing to the origination point, and it's fared as three legs (like the first example above), it's a circle trip. If it's fared as a roundtrip with a stopover, and you're trying to communicate that with a res agent, don't call it a circle trip.

[This message has been edited by Robert Leach (edited 04-17-2003).]