While service is a very important factor related to airline choice, technical factors are also of major consequence. The traveller has consistently reported that convenient scheduling is the most important priority when choosing an airline, as is shown in Table 3.4. While the on-board food and drink provision is placed low in the priority list, it is significant in the decision-making process of airline selection. As such it is an important aspect of the passenger's flying experience as customers expect a satisfactory meal and service. If dissatisfaction occurs, a passenger may select another airline. Table 3.4 also illustrates how passenger priorities may change over time, especially in response to changes in external influences. Security was a key issue in the early 1990s due to aircraft hijackings. By 1999 this was no longer such a concern. 9/11 has almost certainly returned this factor to one of high importance.