$145 Cheap United flights Harrisburg (MDT) to Seattle (SEA)

Apply the "Price (lowest to highest)" filter on Expedia to look for cheap United Airlines return flights from $277 from MDT to SEA. Affordable one-way tickets from $145 are available too.**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 searching one to three months ahead of your departure date to get cheaper fares on United Airlines flights from Harrisburg Intl. Airport (MDT) to Seattle - Tacoma Intl. Airport (SEA). You can save 25% by booking your domestic flight 34 to 86 days in advance versus last-minute reservations made 6 to 12 days out. You could also cut costs by buying your fare on a Sunday, as it's 6% cheaper on average than a Monday, the most expensive day to book.* Nail your timing, and you can enjoy significant savings on domestic trips.*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.

Find United Airlines's earliest flights from MDT to SEA by using our "Morning" and "Early Morning" filters. Not only will you arrive at your destination sooner, early departures also have a 20% less chance of being canceled.**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.

Offering a rewarding loyalty program, United Airlines is a top pick for many travelers heading from MDT to SEA. Plus, if you're a United Mileage Plus and One Key™ member booking through Expedia, you can earn OneKeyCash™* on eligible flights along with your airline miles.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.