If you honestly can't think of ANY questions, you are in trouble...you are likely being too conservative and rehearsing canned interview scenarios/answers...Don't do that! You can't fake this.

Don't you want to know what their average trips are like? What kind of extra training they believe in? How about that you read they are expanding in places like China, India etc? How has this affected the department? fleet changes?

How about asking the people interviewing you what their favorite and least favorite part go the job is?...that one usually gets a few laughs...and it gets people talking, and then they learn you have a personality (this is the goal)

I always liked a guy who knew how to properly ask about the quality of life at a job yet understood that we fly airplanes and go away on (sometimes) lengthy trips. To me it showed he/she has a life and wants to preserve that. I never trusted a blind YES man at an interview....he's likely hiding something that I don't want to find 6-12 months down the line.

Good Luck!