I have sat on both sides of the interview table, it is an imperfect process at best.You would be amazed how a completely innocuous response or comment can rub the wrong person the wrong way. Frontier’s method is no worse or better than anyone else’s, we have the same ratio of 95% decent people to 5% jerks as every other airline.
Like the above posters have said, keep your head up, it happens to almost everyone at some point in their career. Pretty much everyone is hiring and F9 shouldn’t be your premier destination anyway unless you live in one of our bases or are close to retiring and trying to quickly get to the left seat before you punch out. Good luck.