Cheap Spirit Airlines flights Seattle (SEA) to Boston (BOS)

Use the "Price (lowest to highest)" filter on Expedia to find cheap Spirit Airlines round-trip flights from SEA to BOS. Affordable one-way fares 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.

Look for cheap Spirit Airlines flights from Seattle - Tacoma Intl. Airport (SEA) to Logan Intl. Airport (BOS) one to three months ahead of your departure. Travelers who book domestic flights 34 to 86 days in advance can save 25% compared to those who book just 6 to 12 days ahead. No matter the fare type and itinerary, the best day of the week to book a domestic flight is generally Sunday and the most expensive tends to be Monday. Passengers who book on a Sunday can save 6% on average compared to those who book their travel on a Monday.**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 Spirit Airlines's earliest flights from SEA to BOS by checking our "Early Morning" and "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.

With a rewarding loyalty program, Spirit Airlines is a top pick for many passengers heading from SEA to BOS. Plus, if you're a Free Spirit and One Key™ member booking through Expedia, you could earn OneKeyCash™* on eligible flights on top of your airline miles.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.