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

Return flights

14 Sep - 19 Sep	Aer Lingus
08 Sep - 16 Sep	Austrian Airlines
30 Sep - 05 Oct	Icelandair
15 Sep - 19 Sep	Icelandair
29 Sep - 06 Oct	Icelandair
23 Sep - 30 Sep	Icelandair
21 Sep - 28 Sep	Icelandair
09 Sep - 16 Sep	Icelandair
11 Sep - 18 Sep	Icelandair
04 Sep - 11 Sep	Condor	direct
18 Sep - 22 Sep	Air France
24 Sep - 01 Oct	Delta
08 Sep - 15 Sep	Icelandair
30 Sep - 25 Oct	Aer Lingus
28 Sep - 18 Oct	TAP
29 Sep - 25 Oct	Aer Lingus
08 Sep - 04 Oct	Virgin Atlantic
26 Sep - 13 Oct	Aer Lingus
18 Sep - 16 Oct	Condor	direct
30 Sep - 05 Oct	Condor	direct

Also check the deals for one-way flights from Boston 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 Boston to Frankfurt in September from 393€

Return flights