$603 Cheap Swiss International Air Lines flights Philadelphia (PHL) to Kos (KGS)

Scoring cheap one-way SWISS flights from PHL to KGS from $603 on Expedia is simple --- just filter by "Price (lowest to highest)." Or check out our budget-friendly round-trip fares from $804 for your next adventure.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.

Start your search for SWISS flights from PHL to KGS about one month before you want to leave. The cheapest time to reserve an international flight is usually 18 to 29 days ahead of your travel date when you can save 17% versus booking four to five months in advance. No matter your ticket type or itinerary, the best day to book international airfare is usually Sunday. Friday is often the most expensive. Travelers who book on a Sunday can save an average of 17% compared to those who book on a Friday.**Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC's global airline sales database.

Filter your results by "Morning" and "Early Morning" to see the earliest flights from PHL to KGS. Taking off early means flight cancellations are less likely.**Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.

With a 4-star airline rating and a rewarding loyalty program, SWISS is a favorite for many passengers heading from PHL to KGS. What's more, if you're a Swiss Miles & More and One Key™ member booking through Expedia, you could earn OneKeyCash™* on eligible flights on top of your airline miles, which can be used on future travel.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.