Cheapest return flights from Islip to San Juan in September from $254

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

Return flights

14 Sep - 16 Sep Frontier Airlines
15 Sep - 16 Sep Frontier Airlines
16 Sep - 19 Sep Frontier Airlines
17 Sep - 21 Sep Frontier Airlines
09 Sep - 16 Sep Frontier Airlines
25 Sep - 30 Sep Frontier Airlines
26 Sep - 30 Sep Frontier Airlines
19 Sep - 25 Sep Frontier Airlines
26 Sep - 27 Sep Frontier Airlines
17 Sep - 23 Sep Frontier Airlines
29 Sep - 04 Oct Frontier Airlines
24 Sep - 01 Oct Frontier Airlines
15 Sep - 01 Oct Frontier Airlines
28 Sep - 04 Oct Frontier Airlines
15 Sep - 04 Oct Frontier Airlines
06 Sep - 05 Oct Frontier Airlines
30 Sep - 09 Oct Frontier Airlines

Also check the deals for one-way flights from Islip to San Juan in September.

Skyscanner

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.

Book a cheap hotel in San Juan

Cheap car rent in San Juan

Feel free to contact us with any feedback or request another flight research.