AirHint found the following cheapest return flights from Jacksonville (JAX) to San Juan (SJU) in September 2025 (see full year).

Return flights

23 Sep - 30 Sep	Southwest Airlines
24 Sep - 01 Oct	United
25 Sep - 02 Oct	Frontier Airlines
19 Sep - 26 Sep	Frontier Airlines
19 Sep - 21 Sep	Frontier Airlines
19 Sep - 22 Sep	Frontier Airlines
21 Sep - 24 Sep	Frontier Airlines
20 Sep - 27 Sep	United
18 Sep - 21 Sep	Frontier Airlines
17 Sep - 22 Sep	Southwest Airlines
20 Sep - 21 Sep	Breeze Airways

Also check the deals for one-way flights from Jacksonville 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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Cheapest return flights from Jacksonville to San Juan in September from 264€

Return flights