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

Return flights

02 Dec - 09 Dec	Air Canada
02 Dec - 09 Dec	Iberia	direct
07 Dec - 16 Dec	American Airlines
03 Dec - 05 Dec	Aer Lingus
04 Dec - 11 Dec	Air Canada
29 Dec - 24 Jan	Air Canada
10 Dec - 15 Dec	Lufthansa
12 Dec - 27 Jan	British Airways
10 Dec - 14 Dec	British Airways	direct
08 Dec - 14 Dec	Iberia	direct
12 Dec - 24 Dec	Iberia
12 Dec - 25 Dec	British Airways
12 Dec - 09 Jan	Iberia
11 Dec - 13 Jan	Delta
28 Dec - 09 Jan	British Airways
13 Dec - 13 Jan	Air Canada
11 Dec - 13 Jan	Finnair	direct
28 Dec - 17 Jan	British Airways
31 Dec - 07 Jan	British Airways
23 Dec - 17 Jan	British Airways

Also check the deals for one-way flights from Philadelphia to London 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 London in December from $559

Return flights