This is an addendum to the previous element, which calls for centralizing travel with one travel agency. This is important, but in doing so, you need not require travelers to use an online booking system, and you need not require travelers to call the agency directly. By offering travelers the option of doing either, you are accomplishing several goals. You will reduce your fulfillment costs, as online booking is cheaper in terms of a service fee. By giving travelers the option, you are giving them a sense of control, thereby increasing morale and standing a better chance of a high adoption rate.