You don't have a SW seniority number until you show up for class. Anything can happen between now and then that could cause that class date to be delayed or even cancelled. (Terrorism, work action, AD parking 737s, change of business plans due to Brexit, who knows?!)

Until you have that number you are still dating, not married. I'd spend the $300, give Delta your best shot and go to the interview. Then take whichever class date is offered first. If you still want to leave when airline #2 calls, then go for it! (There is no such thing as loyalty in this business. Airlines show no loyalty in return when they have to furlough... and then they raise the retirement age to 65 while thousands are on furlough!)

Personally, Delta has substantially more retirements in the short term, wide body options, and the option of worldwide flying. Options are rare in our career. Give yourself one. Go to the interview. You don't have a decision to make unless you have two job offers with the same class date. [emoji106]