AirHint found the following cheapest return flights from Philadelphia (PHL) to Sofia (SOF) in December 2025 (see full year).

Return flights

02 Dec - 16 Dec	Lufthansa
03 Dec - 16 Dec	Air Canada
31 Dec - 24 Jan	Air Canada
09 Dec - 26 Dec	Lufthansa
30 Dec - 08 Jan	Lufthansa
03 Dec - 17 Dec	Air Canada
10 Dec - 17 Dec	British Airways
24 Dec - 14 Jan	Frontier Airlines
09 Dec - 30 Dec	Lufthansa
11 Dec - 18 Dec	Lufthansa
12 Dec - 09 Jan	Frontier Airlines
10 Dec - 31 Dec	Frontier Airlines
23 Dec - 13 Jan	Spirit Airlines
14 Dec - 28 Dec	Air Canada
25 Dec - 01 Jan	Frontier Airlines
17 Dec - 08 Jan	Aer Lingus
16 Dec - 17 Dec	Aer Lingus
22 Dec - 04 Jan	Frontier Airlines
21 Dec - 04 Jan	Frontier Airlines
20 Dec - 04 Jan	Frontier Airlines

Also check the deals for one-way flights from Philadelphia to Sofia in December.

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 Philadelphia to Sofia in December from $447

Return flights