The most important part of any interview with an airline is showing that you care passionately about giving great customer service. The most important thing you need to get across in your interview is that you LOVE working in a customer orientated industry and you strive at all times to make your customers happy.
The majority of the interview is designed to find if you understand what good customer service is, how you work in a team ie. if you have been supportive to colleagues etc., if you have the ability to learn from feedback you have received in the past and that you understand what the job entails.
You need to go to your interview armed with examples of when and how you gave exceptional customer service and when you have worked in a team to make something happen for your customers.
That is the best advice I can give you. Just relax and let your personality shine through. If you have thought through all of the above before you get there, you will feel more relaxed and your answers to any questions will just come naturally.
Remember that most large companies nowadays ask you to give examples of how you worked in your previous employment, in different situations and they use your answers to work out if you understand what good customer service is etc. So it is important to have really good examples of great customer service, when you went above and beyond what would be thought of as normal.
Good luck.