DAL loves military and if you are on your way out they will want to talk to you. Nuf said. We love military. Period. Not all get through. I would recommend that you do the prep and Emerald Coast. It is by far the best way to prepare for this interview.
DAL will not normally call a military guy for an interview until it will mesh with your discharge papers and ability to roll right in the job here. It is not that they do not love you, it is just that there is no reason to offer you an interview slot when it can be done later.