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

Return flights

03 Sep - 17 Sep	Air Canada
10 Sep - 24 Sep	Air Canada
24 Sep - 01 Oct	Air Canada
24 Sep - 30 Sep	Air Canada
09 Sep - 30 Sep	Air Canada
14 Sep - 22 Sep	Air Canada
02 Sep - 09 Sep	Aer Lingus
30 Sep - 06 Oct	Air Canada
01 Sep - 08 Sep	Finnair
25 Sep - 11 Oct	Air Canada
18 Sep - 21 Sep	Air Canada
05 Sep - 14 Sep	Air Canada
15 Sep - 22 Sep	Air Canada
30 Sep - 07 Oct	United
27 Sep - 04 Oct	United
30 Sep - 07 Oct	British Airways	direct
30 Sep - 06 Oct	British Airways	direct
27 Sep - 04 Oct	British Airways	direct
25 Sep - 11 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 $503

Return flights