Cheap flights from Seattle to Illinois from $159

The cheapest month to fly to Illinois from Seattle is in February. Flight prices, which tend to average around $257, are often lower during this time because this is during the off-season. If you aren’t able to travel to Illinois during the month of February, then flying in January is also cheap. Prices for this month can be found on momondo for an average of $287.

The cheapest day to depart from Seattle to Illinois is on a Thursday when prices can be found for as low as $441. Flights from Seattle to Illinois on a Sunday will generally be more expensive and average around $549. Keep in mind that these prices on both days could fluctuate depending on the season and the demand.

Our most recent data shows that the best time of day to fly to Illinois is in the afternoon. Flights from Seattle to Illinois during this time can be as low as $392. Flights at noon are often more expensive with an average ticket price of $496.

Fly from Seattle/Tacoma Intl to Chicago Midway for the best Seattle/Tacoma Intl - Illinois flight prices

You are more likely to see cheaper flights to Illinois from Seattle when booking weeks ahead of your departure date. In general, you can expect to find flights to Illinois for around $358 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Illinois from Seattle for as low as $312 on momondo.

There are 4 cabin classes available to choose from on Seattle to Illinois flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

Frontier, American Airlines, and Delta are the most popular carriers operating from Seattle/Tacoma Intl to Illinois

American Airlines, Alaska Airlines and United Airlines are the top three most popular airlines that fly to Illinois from Seattle according to our data. American Airlines is the first choice among our users, with 29% of people opting to fly with this airline when traveling to Illinois. Keep in mind that there are 6 different airlines that fly to Illinois on a routine basis, so you have a few additional options to choose from.

The number of flights available between Seattle and Illinois is 20 per day as of November 2026. The most frequent departure time is 10:00AM, with 61% of daily flights leaving at noon.

As of November 2026, 140 flights take off from Seattle and land in Illinois each week. The most common flight departure day for this route is Sun, with 30% of weekly flights taking off on this day.