To prep with a formal company or not depends on your background. If you have extensive experience conducting STAR interviews yourself or have been through many HR interviews before in passed jobs you may be just fine. The key is to be very specific, complete your thoughts , and make sure you give details in your actions. Never use the words I always , usually , sometimes etc... Take a minute to think before answering during the interview no matter how prepared you are. I think people get thrown a curveball with some of the questions because they didn’t have a story prepared and then just spit out whatever comes to mind. It is ok to take your time. A minute to you will feel a lot slower than a minute to the interviews as they expect you to think and be methodical as we are on the flight deck.