AirHint found the following cheapest return flights from Seattle (SEA) to Mexico City (MEX) in September 2025 (see full year).

Return flights

19 Sep - 21 Sep	Volaris
26 Sep - 28 Sep	Volaris
25 Sep - 28 Sep	Volaris
14 Sep - 21 Sep	Volaris
15 Sep - 19 Sep	Volaris
11 Sep - 14 Sep	Volaris
17 Sep - 22 Sep	Volaris
01 Sep - 02 Sep	Volaris
17 Sep - 21 Sep	Hawaiian Airlines
18 Sep - 21 Sep	Hawaiian Airlines

Also check the deals for one-way flights from Seattle to Mexico City 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 return flights from Seattle to Mexico City in September from 283€

Return flights