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

Return flights

21 Sep - 25 Sep	United	direct
26 Sep - 30 Sep	United	direct
25 Sep - 29 Sep	United
16 Sep - 30 Sep	United
14 Sep - 20 Sep	United
30 Sep - 14 Oct	United
17 Sep - 01 Oct	United
19 Sep - 03 Oct	United
20 Sep - 04 Oct	United
25 Sep - 09 Oct	United
09 Sep - 23 Sep	United
19 Sep - 23 Sep	United
22 Sep - 06 Oct	United
03 Sep - 17 Sep	United
02 Sep - 05 Sep	United
19 Sep - 21 Sep	United
23 Sep - 07 Oct	United
24 Sep - 08 Oct	United
21 Sep - 05 Oct	United

Also check the deals for one-way flights from Washington 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 Washington to San Juan in September from 132€

Return flights