Oh, I just thought of a way:
The user has entered a new itinerary via the Prepare Itinerary use case.
The user submits the itinerary. Once in the Pay for Itinerary use case, the user doesn't select to pay with credit card; instead, the user selects award travel, ...
A similar scenario can exist with the Change Itinerary use case.
Hmmm...it is simple.
Thanks for the discussion.
-Ravi