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

Return flights

23 Sep - 29 Sep	Volaris El Salvador
26 Sep - 02 Oct	United
29 Sep - 29 Sep	Avianca
29 Sep - 07 Oct	Avianca
24 Sep - 30 Sep	Volaris El Salvador
26 Sep - 30 Sep	Avianca
20 Sep - 22 Sep	Copa
19 Sep - 21 Sep	Copa
28 Sep - 28 Sep	Copa
18 Sep - 21 Sep	Copa
20 Sep - 27 Sep	Copa
22 Sep - 30 Sep	Avianca
30 Sep - 07 Oct	Avianca
30 Sep - 14 Oct	Avianca
23 Sep - 07 Oct	Avianca
29 Sep - 08 Oct	Avianca

Also check the deals for one-way flights from Washington to San Jose 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.

Book a cheap hotel in San Jose

Cheap car rent in San Jose

Cheapest return flights from Washington to San Jose in September from $235

Return flights