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

Return flights

02 Sep - 09 Sep	Porter Airlines (Canada) Ltd
23 Sep - 30 Sep	Porter Airlines (Canada) Ltd
21 Sep - 28 Sep	Air Transat
16 Sep - 23 Sep	Air Transat
19 Sep - 26 Sep	FrenchBee
09 Sep - 16 Sep	Air Transat
17 Sep - 24 Sep	FrenchBee
11 Sep - 12 Oct	Air Transat
11 Sep - 13 Oct	Air Transat
20 Sep - 27 Sep	Air Transat
01 Sep - 08 Sep	Air Transat
30 Sep - 07 Oct	Air Transat
14 Sep - 21 Sep	Air Transat
24 Sep - 01 Oct	Air Transat
25 Sep - 02 Oct	Air Transat
11 Sep - 10 Oct	Air Transat
29 Sep - 06 Oct	FrenchBee
14 Sep - 10 Oct	Air Transat
28 Sep - 05 Oct	Air Transat
27 Sep - 04 Oct	Air Transat

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 564€

Return flights