I know it's easier said than done, but just be patient. It was just under 3 weeks for me to get my answer (over a year and a half ago). And when they did, they offered me a class in 8 days! It's usually a good thing that they take a while to get back to you... Preliminary background checks, drug test results, sifting through the folks that made it through the initial, etc. It all takes time. They don't invest that time and expense usually unless you're all but hired.
With few exceptions, Mesaba isn't very quick about getting back to you after the interview. It's just the way it is. It's still a good place to be with some great people.
Good luck!
CS