Cheapest return flights from Islip to San Juan in December from $201

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

Return flights

06 Dec - 11 Dec Frontier Airlines
11 Dec - 15 Dec Frontier Airlines
10 Dec - 15 Dec Frontier Airlines
13 Dec - 16 Dec Frontier Airlines
06 Dec - 10 Dec Frontier Airlines
13 Dec - 17 Dec Frontier Airlines
15 Dec - 16 Dec Frontier Airlines
11 Dec - 16 Dec Frontier Airlines
08 Dec - 13 Dec Frontier Airlines
12 Dec - 17 Dec Frontier Airlines
14 Dec - 18 Jan Frontier Airlines
31 Dec - 11 Jan Frontier Airlines
19 Dec - 11 Jan Frontier Airlines
31 Dec - 07 Jan Frontier Airlines
30 Dec - 09 Jan Frontier Airlines
25 Dec - 01 Jan Frontier Airlines
24 Dec - 01 Jan Frontier Airlines
23 Dec - 01 Jan Frontier Airlines
31 Dec - 05 Jan Frontier Airlines
31 Dec - 04 Jan Frontier Airlines

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

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