Having been through a similar process recently, I would recommend doing some reading on the airline in question here on FT and then PMing a few of the folks that really seem to know their material or that either work for or have been interviewed by the carrier if possible. If you've been to any DOs, you may also want to contact some folks that you've met that are top tier on the airline and that know it's operations well. Luckily I had the advantage of being able to contact both an FTer that had recently been hired by the airline that I was meeting with as well as another who had just gone through a similar interview. After messaging with them I was able to feel more confident about the interview process and some of the things to prepare.

Good luck!