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

Return flights

21 Sep - 07 Oct	jetBlue
02 Sep - 09 Sep	jetBlue
08 Sep - 18 Sep	jetBlue
25 Sep - 18 Oct	Lufthansa
30 Sep - 07 Oct	Aer Lingus
29 Sep - 06 Oct	jetBlue
10 Sep - 17 Sep	Aer Lingus
06 Sep - 20 Sep	jetBlue
23 Sep - 30 Sep	United
24 Sep - 01 Oct	United
07 Sep - 16 Sep	United
23 Sep - 01 Oct	United
10 Sep - 24 Sep	United
15 Sep - 20 Sep	jetBlue
23 Sep - 30 Sep	British Airways	direct
10 Sep - 17 Sep	British Airways	direct
24 Sep - 01 Oct	British Airways	direct
30 Sep - 07 Oct	British Airways	direct
23 Sep - 01 Oct	British Airways	direct
21 Sep - 07 Oct	British Airways	direct

Also check the deals for one-way flights from Philadelphia to London 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 Philadelphia to London in September from 508€

Return flights