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

Return flights

05 Dec - 12 Dec	United
15 Dec - 22 Dec	United
24 Dec - 09 Jan	Lufthansa
22 Dec - 13 Jan	Air Canada
05 Dec - 12 Dec	British Airways	direct
24 Dec - 09 Jan	Finnair	direct
24 Dec - 31 Dec	TAP
22 Dec - 13 Jan	Finnair	direct
22 Dec - 02 Jan	Air Canada
24 Dec - 31 Dec	Iberia	direct
25 Dec - 01 Jan	United
19 Dec - 26 Dec	British Airways
18 Dec - 30 Dec	United
25 Dec - 01 Jan	British Airways	direct
19 Dec - 26 Dec	Finnair	direct
18 Dec - 28 Dec	British Airways
18 Dec - 28 Dec	Iberia	direct
20 Dec - 01 Jan	Air Canada
18 Dec - 04 Jan	Scandinavian Airlines
22 Dec - 02 Jan	British Airways	direct

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 $633

Return flights