They don't expect you to be a guru of aircraft. Have a good understanding of the principles of flight, what each aircraft looks like, the main differences between Boeing and Airbus. Also, a good knowledge of the industry and the business / management side of flying is a great help.
I wouldn't worry about what they are going to ask you. It's likely they'll ask you something that you had no idea they were going to ask you...something that makes you actually sit there and think before answering rather than reading off rehearsed lines. The more you get hooked up on learning each question you think they'll ask, the more likely you'll do badly on the ones that really count - the ones they know you won't really have prepared a specific answer for.