This is live pricing from Travelpayouts' aggregation of 40+ booking engines. The $518 fare is the cheapest current round-trip from Philadelphia (PHL) to SEA on Southwest flight WN3112, departing 2026-06-17 at 16:35 with return on 2026-06-19.

Clicking "Book this flight" opens Kiwi.com with this exact flight pre-filtered — same airline, same dates, same passenger count.