AirHint found the following cheapest return flights from St. Louis (STL) to San Juan (SJU) in September 2025 (see full year).
Return flights
| 22 Sep - 26 Sep | Frontier Airlines | ||
| 19 Sep - 21 Sep | Frontier Airlines | ||
| 11 Sep - 18 Sep | Frontier Airlines | ||
| 09 Sep - 12 Sep | Frontier Airlines | ||
| 11 Sep - 15 Sep | Frontier Airlines |
Also check the deals for one-way flights from St. Louis to San Juan 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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