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

Return flights

29 Sep - 06 Oct	Scandinavian Airlines
05 Sep - 12 Sep	Icelandair
25 Sep - 02 Oct	Scandinavian Airlines
01 Sep - 08 Sep	Lufthansa
02 Sep - 09 Sep	Lufthansa
07 Sep - 14 Sep	Lufthansa
08 Sep - 15 Sep	Lufthansa
09 Sep - 16 Sep	Lufthansa
14 Sep - 21 Sep	Lufthansa
11 Sep - 19 Sep	Lufthansa
11 Sep - 20 Sep	Lufthansa
23 Sep - 30 Sep	Scandinavian Airlines
27 Sep - 04 Oct	Scandinavian Airlines

Also check the deals for one-way flights from Washington to Oslo 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 Oslo in September from 356€

Return flights