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

Return flights

31 Dec - 13 Jan	Frontier Airlines
27 Dec - 29 Dec	Copa
30 Dec - 12 Jan	Allegiant Air
30 Dec - 08 Jan	Frontier Airlines
28 Dec - 13 Jan	Delta
30 Dec - 06 Jan	Delta
28 Dec - 01 Jan	United
29 Dec - 06 Jan	Delta
28 Dec - 06 Jan	Delta
29 Dec - 07 Jan	Avianca
31 Dec - 07 Jan	Delta
27 Dec - 29 Dec	Avianca	direct

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

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 Jose in December from 285€

Return flights