$555 Cheap KLM flights St. Louis (STL) to Southampton (SOU)

Grab cheap round-trip KLM flights from $941 from STL to SOU by filtering your results from "Price (lowest to highest)" on Expedia. Or look for options from $555 for a one-way journey.**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.

Check for KLM flights from STL to SOU about one month before you want to leave. The most affordable time to reserve an international flight is generally 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 can be the most expensive. Travelers who book on a Sunday can save 17% on average 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 "Early Morning" and "Morning" to browse the earliest departures from STL to SOU. Leaving 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.

A 4-star airline rating and the chance to rack up points through KLM Flying Blue are the start of the reasons to leave from STL to SOU with KLM. Plus, when you join Expedia's free One Key™ program, you can earn OneKeyCash™* alongside any airline loyalty program earnings. You can put it toward your future trips.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.