AirHint found the following cheapest return flights from Portland (PDX) to San Francisco (SFO) in September 2025 (see full year).

Return flights

06 Sep - 08 Sep	Hawaiian Airlines	direct
03 Sep - 10 Sep	Hawaiian Airlines	direct
03 Sep - 06 Sep	United	direct
23 Sep - 30 Sep	United	direct
25 Sep - 29 Sep	United	direct
24 Sep - 28 Sep	United	direct
17 Sep - 21 Sep	United	direct
08 Sep - 12 Sep	United	direct
07 Sep - 10 Sep	United	direct
30 Sep - 10 Oct	United	direct
26 Sep - 28 Sep	United	direct

Also check the deals for one-way flights from Portland to San Francisco 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 Portland to San Francisco in September from 57€

Return flights