AirHint found the following cheapest return flights from Philadelphia (PHL) to Lisbon (LIS) in August 2025 (see full year).

Return flights

11 Aug - 20 Aug	Aer Lingus
20 Aug - 28 Aug	Spirit Airlines
01 Aug - 29 Aug	Spirit Airlines
22 Aug - 31 Aug	Aer Lingus
11 Aug - 19 Aug	Iberia	direct
19 Aug - 28 Aug	American Airlines	direct
11 Aug - 20 Aug	American Airlines	direct
10 Aug - 20 Aug	American Airlines	direct
09 Aug - 19 Aug	TAP
27 Aug - 06 Sep	TAP
09 Aug - 20 Aug	TAP
29 Aug - 01 Sep	TAP
14 Aug - 01 Sep	American Airlines	direct
27 Aug - 03 Sep	United
25 Aug - 01 Sep	United
30 Aug - 06 Sep	United
29 Aug - 01 Sep	Finnair	direct

Also check the deals for one-way flights from Philadelphia to Lisbon in August.

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 Lisbon in August from $573

Return flights