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

Return flights

26 Sep - 07 Oct	FrenchBee
29 Sep - 06 Oct	FrenchBee
30 Sep - 10 Oct	Porter Airlines (Canada) Ltd
28 Sep - 05 Oct	FrenchBee
30 Sep - 07 Oct	Air Transat
24 Sep - 01 Oct	FrenchBee
26 Sep - 03 Oct	FrenchBee
22 Sep - 29 Sep	FrenchBee
23 Sep - 30 Sep	Air Transat
27 Sep - 29 Sep	Air Transat
25 Sep - 02 Oct	Air Transat
27 Sep - 04 Oct	Air Transat
21 Sep - 28 Sep	FrenchBee
27 Sep - 18 Oct	Air Transat
20 Sep - 27 Sep	Air Transat
19 Sep - 26 Sep	FrenchBee

Also check the deals for one-way flights from Montreal 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 Montreal to Sofia in September from 522€

Return flights