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

Return flights

10 Aug - 11 Aug	Frontier Airlines
15 Aug - 21 Aug	United
17 Aug - 24 Aug	Air Canada
25 Aug - 28 Aug	Spirit Airlines
11 Aug - 18 Aug	United
10 Aug - 16 Aug	Frontier Airlines
11 Aug - 14 Aug	Frontier Airlines

Also check the deals for one-way flights from Philadelphia to Keflavik 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 Keflavik in August from 350€

Return flights