AirHint found the following cheapest return flights from Chicago (MDW) to St. Louis (STL) in September 2025 (see full year).
Return flights
| 09 Sep - 16 Sep | Delta | ||
| 07 Sep - 07 Sep | Frontier Airlines | ||
| 07 Sep - 07 Sep | Southwest Airlines | direct |
Also check the deals for one-way flights from Chicago to St. Louis in September.
The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.
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