I think persistence of paid itineraries will be required, how else will you go about storing details of the itinerary, which you will obviously need later on (at least till the passenger has flown to his destination).
Steven, To my understanding, both paid and unpaid itineraries needs to be persisted...."How long" and "to what extent" is ur call....for the exam persisting paid itineraries will suffice.Imagine u running a travel agency with 20 agents and an online customer
website. Bulk of ur transactions happen via travel agents. u would definitely want to know how much sale a particular agent(in seats/class/dollar value terms) made this season...this is ur primary business and hence makes sense to persist paid itineraries. It would also help resolving discrepancies, if any.
For intelligence/reporting format, sometimes unpaid itineraries are needed...u would like to track customers vis-a-vis their itineraries and indentify a preference pattern for later marketing activies (newsletters and/or promotions).
where to store is again ur choice....could be db or flat file or an archive db...since the exam restricts ur choice of hardware choice, u might only want to persist the paid itineraries. But whatever u do, u need to mention it explicity in the assumption section. Hope that helps