AirHint found the following cheapest return flights from Denver (DEN) to Frankfurt (FRA) in September 2025 (see full year).

Return flights

04 Sep - 11 Sep	Icelandair
01 Sep - 08 Sep	Icelandair
07 Sep - 14 Sep	Icelandair
10 Sep - 17 Sep	United	direct
25 Sep - 29 Sep	Icelandair
16 Sep - 23 Sep	United	direct
04 Sep - 11 Sep	Lufthansa	direct
01 Sep - 08 Sep	Lufthansa	direct
22 Sep - 29 Sep	United	direct
28 Sep - 05 Oct	United
25 Sep - 02 Oct	United
13 Sep - 20 Sep	United
26 Sep - 04 Oct	United

Also check the deals for one-way flights from Denver to Frankfurt 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 Denver to Frankfurt in September from 590€

Return flights