| Nonstop Flights: Austin to/from St. Louis $180 r/t [June-September] â American Airlines / Alaska Airlines American and Alaska Airlines have round-trip flights from Austin (AUS) to St. Louis (STL) for $180, NONSTOP. Flights June to September. Very few extended weekends available. Origin/Destination reversible. Main Cabin. Not Basic. A Carry-on bag, seat selection, and also a personal item is allowed for free. Click for more details and booking links Nonstop Flights: Austin to/from St. Louis $180 r/t [June-September] â American Airlines / Alaska Airlines . | 