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

Return flights

03 Dec - 17 Dec	Aer Lingus
08 Dec - 22 Dec	Air Canada
09 Dec - 16 Dec	United
03 Dec - 17 Dec	British Airways	direct
09 Dec - 16 Dec	British Airways	direct
09 Dec - 19 Dec	Aer Lingus
04 Dec - 11 Dec	Aer Lingus
11 Dec - 25 Dec	British Airways
09 Dec - 19 Dec	British Airways	direct
11 Dec - 15 Dec	Aer Lingus
29 Dec - 05 Jan	British Airways
22 Dec - 05 Jan	Air Canada
27 Dec - 02 Jan	Air Canada
22 Dec - 05 Jan	Iberia	direct
18 Dec - 03 Jan	Delta

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 553€

Return flights