DTW is served by NWA, SWA, AA, UAL, but not proair. Pro flies into Detroit City which is farther than DTW. Proair is also has not had the best reputation from the city of detroit. I heard that they don't takeoff sometimes if they don't have enough people to fill the plane. Just a bunch of small airline stuff. Just try using NWA the major airline of detroit or the soon to become major airline AA.
Good luck and best flying wishes!!