While nothing in the application process is guaranteed, and saying you are or aren't qualified for the prep school (Meaning the one at the academy) is a pretty finite comment, the post by CannotBeDisplayed isn't one that should be criticized too much.
I'll tell you that there are quite a few applicants that while I won't go as far as saying they "Don't Qualify" for the prep school; the chances of them getting a prep school slot would be very difficult. E.g. if you have a 3.9 gpa, 28-30 ACT, top-10 (Not top 10%) of your class, has all the leadership, EC, sports, etc... are NOT a recruited athlete or minority, etc.... (List not all inclusive), then you would be hard pressed to receive a prep school slot. The prep school is not where number 1101- 1300 on the appointment list go. (Assuming they accepted 1100 appointees). Receiving a prep school offer is just as complicated as receiving an appointment. Traditionally, the prep school slots are used for individuals who the air force sees potential in, but there are areas in their application/life that the prep school can help them with. There are definitely some whereby the prep school really isn't for them.
As for having "Back up" plans, you most definitely should. And how much determination and how much you want to attend the academy, has no bearing on whether or not you will get to attend. If attending the air force academy and becoming a commissioned officer is truly what you want, then that's all you have to tell the nomination panel. "If I don't receive an appointment this year, I will continue to do whatever I can to keep the academy an option for me". But the reality is; while some individuals have attended the academy even after completing a complete 4 year degree at a civilian school, there's going to be many who by the time they've finished their 2nd year at a civilian university, will realize (For Them), that going to the academy is no longer practical.
CannotBeDisplayed said: "I will go to my top choice civilian school. I think if you can afford it, it's very worth it to go to the school you want to attend. Whether you apply the next year or not, you may not get in. You might as well continue on as if you had never heard of a service academy. You can't depend on something uncertain."
There's a lot of truth to this. Most individuals who are truly qualified for the air force academy are usually also the type who can get accepted to some of the best colleges in the country. If you don't receive an appointment to the academy, but get accepted to your top civilian school choice, you should definitely accept and attend that school. Play the "reapply" card one day at a time. Just because you want the academy doesn't mean if you don't get it this year, that you should turn down a high end school and possibly scholarship, so you can attend a junior college for a year while you're re-applying. You can definitely reapply to the academy if you don't receive your appointment out of high school. That doesn't mean you should turn down other excellent opportunities. Doesn't matter if you attend a junior college, university of wherever, Harvard, Purdue, W&M, etc... Take advantage of the opportunities given you. If you decide to reapply, then do so. That's a personal choice. But you can do that from any school. And no... you can't depend on receiving an appointment. An appointment is definitely uncertain. The reason for "Plan B" schools is in case you don't receive an appointment. You can't just assume that if you apply enough times, you'll eventually receive an appointment. Maybe you won't. Individuals need to keep all of their options open.