AirHint found the following cheapest one-way flights from St. Louis (STL) to Cancun (CUN) in September 2025 (see full year).

One-Way flights

08 Sep	Frontier Airlines	direct
14 Sep	Frontier Airlines	direct
23 Sep	Frontier Airlines	direct
29 Sep	Frontier Airlines	direct
21 Sep	Frontier Airlines	direct
05 Sep	Frontier Airlines	direct
11 Sep	Frontier Airlines	direct
26 Sep	Frontier Airlines	direct
10 Sep	Frontier Airlines	direct
02 Sep	Frontier Airlines	direct

Also check the deals for return flights from St. Louis to Cancun 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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Cheapest one-way flights from St. Louis to Cancun in September from 97€

One-Way flights