Cheapest one-way flights from Islip to San Juan in September from $127

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

One-Way flights

30 Sep Frontier Airlines
27 Sep Frontier Airlines
13 Sep Frontier Airlines
26 Sep Frontier Airlines
09 Sep Frontier Airlines
06 Sep Frontier Airlines
05 Sep Frontier Airlines
07 Sep Frontier Airlines
17 Sep Frontier Airlines
21 Sep Frontier Airlines

Also check the deals for return 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.

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