The billing procedure should be as clear but at the same time as easy as possible. The Online purchase of flights is very common lately. However a high number of customers are still skeptical with reveling their bank de- tails online, so it is very important to design the billing procedures as clear and easy understandable as possible. As for the brick and mortar agencies the bill should be standardized in order to impose consistency among the different independent agen- cies. Being B.A. a traditional carrier the price of the ticket include almost all the ex- tra like inboard food and entertainment while low-cost companies base their strat- 6