Delta has round-trip flights from Austin (AUS) to Detroit (DTW) for $137-$167, NONSTOP. Flights August to March. Extended Weekends available. Cheapest flights on Delta are on Tuesdays and Wednesdays.
Spirit and Frontier have flights available starting at $71 from August to October.
Note: Carry-on bag is allowed for free on Delta. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.
Note: Spirit and Frontier fares do not include a free carry-on bag. Only a small personal item, like a Jansport City Scout backpackĀ is free. You can avoid paying for seat selection if you accept the randomly assigned seat prior to boarding.
Note: Spirit and Frontier seats only have 28-inches of pitch; 2-to-3 inches less space than most other airlines.
Click for more details and booking links Nonstop Flights: Austin to Detroit $71-$167 r/t – Spirit / Delta