I believe that everyone should do some kind of prep. Getting prepped for an interview is not about "canned answers" to questions. It is about taking your experiences and making them relevant to what the employer seeks in a candidate. For instance, an airline interview is way different than a corporate interview.
Interview prep is not just for airline people either. I had a CEO of a State Fair operation that was being interviewed for another State Fair and Off-Track betting operation. His questions that were being asked were WAY different than the common person in an entry-level to mid-management job. Prior to prepping him, I asked him to send me a list of questions that he had previously been asked in other interviews.
One of the questions he had been asked was whether he had ever run an off track betting operation. I then asked him what his answer was. He told me he told them "no" and then waited for the next question. I pointed out to him that while he had never run an OTB operation, that with his background in dealing with government regulatory agencies, he most certainly had some qualities that he could state that were similar in nature. He had not thought about this and then could see how he could expand his answer based upon his background.
I think that interview prep is valuable because sometimes an outside 3rd party can see what you have in your background that perhaps you cannot see yourself.
I want to throw in a plug for Albie (Aaron). The other day I was working with a client who had just interviewed with a company and had not gotten the position. We believed that the main sticking point was why he was leaving his current employer. He has been with his employer for over 8 years, which sometimes in the aviation world is the kiss of death. Not only is this pilot dealing with the tough aviation business right now, but also the fact that he makes a good sum of money in his current position. This particular employer is one that puts convenience before safety, in addition to not placing value on the professionalism of this pilot. But, how do you say that best without dogging the employer?
I called Aaron for a "second opinion." During this call, I had my client on the line, so that he could hear what Aaron had to say. Let me tell you, Aaron is the real deal. He spoke to us for about 40 minutes and his advice on how to answer this question was right on target. It was worth every penny that this client of mine paid.
I have suggested to my client that he prep fully with Aaron and spend the $300. To him, after hearing Aaron's answers, he could definately see the value for the money. Never once did Aaron give him a "canned answer." He helped my client answer the question based upon his background.
By the way, no amount of preparation can turn someone into an "angel" that is a "devil" by nature!

What it does do is help people to feel confident about the answers they are giving and to understand the psychology of what goes on from the Hiring Manager perspective.
People do have a choice if they want to prep or not. But I will say that with the aviation job market being so tight, it would be the best advice I could give to any of my clients.
For what it is worth, when my clients ask about interview prep, I can tell whether they will have a problem answering interview questions based upon how they answer the questions about their position responsibilities for their resume. If they can articulate the answers to me while I am asking about their current and previous jobs, I see no reason to even suggest it.
Kathy