$151 Cheap United flights St. Louis (STL) to Harrisburg (MDT)

Grab cheap return United Airlines flights from $249 from STL to MDT by filtering your results from "Price (lowest to highest)" on Expedia. Or look for bargains from $151 for a one-way trip.**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.

To find cheap United Airlines fares from Lambert-St. Louis Intl. Airport (STL) to Harrisburg Intl. Airport (MDT), start searching one to three months before your intended departure. Securing domestic flights 34 to 86 days in advance could save you 25% compared to booking just 6 to 12 days ahead. The day you book can also affect the overall cost. Sunday is generally the most affordable, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking your flight on a Sunday.**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 departures from STL to MDT. Setting 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.

Travel from STL to MDT with United Airlines and you can look forward to a range of perks starting with a rewarding loyalty program. When booking through Expedia as a United Mileage Plus and One Key™ member, you could also earn OneKeyCash™* to spend on select future travel purchases.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.