AirHint found the following cheapest return flights from London (LHR) to Sofia (SOF) in September 2025 (see full year).

Return flights

30 Sep - 11 Oct	Vueling Airlines
30 Sep - 28 Oct	SWISS
29 Sep - 01 Oct	SWISS
26 Sep - 30 Sep	SWISS
26 Sep - 29 Sep	SWISS
30 Sep - 04 Oct	SWISS
30 Sep - 19 Oct	SWISS
30 Sep - 02 Oct	SWISS
26 Sep - 03 Oct	SWISS
29 Sep - 03 Oct	SWISS
23 Sep - 01 Oct	SWISS
24 Sep - 01 Oct	SWISS
24 Sep - 27 Sep	SWISS
23 Sep - 30 Sep	SWISS
24 Sep - 29 Sep	SWISS
27 Sep - 30 Sep	Austrian Airlines
27 Sep - 29 Sep	Austrian Airlines
26 Sep - 27 Sep	SWISS
23 Sep - 27 Sep	SWISS
30 Sep - 30 Sep	Austrian Airlines

Also check the deals for one-way flights from London to Sofia 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 London to Sofia in September from 158€

Return flights