I would not get discouraged by the TBNT letters. They announced that everyone who applied in 2014 would get one. Also be aware that any possible typo in the application process can automatically "trigger" one of these letters. For example, if you forget to check a simple block or answer a question like "are you 18 or older?"
Not sure if this is specific to Frontier's online app. But you get the idea.

I would reapply and go to the job fairs till they say yes or no in person. This seems to be the best route if your serious.