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$66+ Cheap flights from Seattle (SEA) to Illinois

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 10/22. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — ORD
Oct 17 — Oct 241
Fri 10/17
Fri 10/24
1 adult, Economy
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Cheap flight deals from Seattle to Illinois

Keep the following information in mind while searching for Seattle to Illinois flight deals. Data was last updated September 17, 2025.

Round-trip from

$188
(Frontier)

One-way from

$66
(Trip.com)

Popular in

December

Cheapest in

January

Average price

$290

Good round-trip deal

$268 or less

Good one-way deal

$167 or less
From Seattle/Tacoma Intl to Illinois
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One-way flight from Seattle/Tacoma Intl to Illinois
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Highest demand for flights based on searches. 5% potential increase in price ($15 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease ($9 potential savings vs. average RT price).
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Average for round-trip flights in September 2025
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Price to beat on a round-trip flight from Seattle/Tacoma Intl to Illinois.
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Price to beat on a one-way flight from Seattle/Tacoma Intl to Illinois.
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Find flight deals from Seattle to Illinois

Cheapest flights from Seattle to Illinois
Explore the most affordable flight options available from Seattle to Illinois. Find the lowest fares from popular airlines and budget airlines, with prices last updated on September 17, 2025.

This Frontier deal was found by Cheapflights users on 9/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/278:43 pmSEA - STL
1 stop10h 24mFrontier
Thu 10/308:40 pmSTL - SEA
2 stops18h 57mFrontier
Deal found 9/15$188
This Kiwi.com deal was found by Cheapflights users on 9/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/316:15 pmSEA - ORD
Nonstop4h 09mMultiple Airlines
Fri 11/76:00 amORD - SEA
1 stop8h 13mMultiple Airlines
Deal found 9/16$190
This Kiwi.com deal was found by Cheapflights users on 9/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 10/56:12 amSEA - STL
1 stop24h 54mFrontier
Tue 10/77:52 pmSTL - SEA
1 stop18h 15mFrontier
Deal found 9/16$190
This Kiwi.com deal was found by Cheapflights users on 9/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/252:43 pmSEA - ORD
Nonstop4h 07mHawaiian Airlines
Fri 10/318:00 amORD - SEA
Nonstop4h 44mHawaiian Airlines
Deal found 9/14$191
This Booking.com deal was found by Cheapflights users on 9/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/36:12 amSEA - STL
1 stop24h 54mFrontier
Mon 10/67:55 pmSTL - SEA
1 stop18h 12mFrontier
Deal found 9/17$191
This Mytrip deal was found by Cheapflights users on 9/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/2410:16 amSEA - MDW
1 stop11h 04mFrontier
Sun 10/266:24 pmMDW - SEA
1 stop19h 43mFrontier
Deal found 9/16$191
This Delta deal was found by Cheapflights users on 9/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 12/35:55 pmSEA - ORD
Nonstop4h 04mDelta
Fri 12/55:03 pmORD - SEA
1 stop7h 11mDelta
Deal found 9/16$192
This Kiwi.com deal was found by Cheapflights users on 9/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/255:55 pmSEA - ORD
Nonstop4h 11mAlaska Airlines
Fri 10/319:20 amORD - SEA
1 stop9h 45mAlaska Airlines
Deal found 9/14$193
This Kiwi.com deal was found by Cheapflights users on 9/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/188:43 pmSEA - STL
1 stop10h 24mFrontier
Tue 10/217:52 pmSTL - SEA
1 stop18h 15mFrontier
Deal found 9/15$194
This Southwest deal was found by Cheapflights users on 9/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/255:45 amSEA - MDW
Nonstop4h 00mSouthwest
Fri 10/319:05 amMDW - SEA
Nonstop4h 35mSouthwest
Deal found 9/17$194
This American Airlines deal was found by Cheapflights users on 9/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/2510:39 amSEA - ORD
Nonstop4h 21mAmerican Airlines
Fri 10/3111:05 amORD - SEA
Nonstop4h 41mAmerican Airlines
Deal found 9/16$195
This Trip.com deal was found by Cheapflights users on 9/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/36:12 amSEA - STL
1 stop24h 54mFrontier
Sun 10/57:55 pmSTL - SEA
1 stop6h 35mFrontier
Deal found 9/14$195

Cheapflights Fare Finder

 
Customize your flight search to find flights from Seattle to Illinois that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated September 17, 2025.
Use the filters below to find and compare flights from Seattle to Illinois that are best for you.

Fly from

Seattle

Fly to

Illinois

Route

Depart

Return

Price

SeattleChicago

SEA - ORD

SEAORD

Seattle/Tacoma Intl

Thu 11/27

10:53 am-5:06 pm

Nonstop4h 13m

Chicago O'Hare Intl

Wed 12/3

8:00 am-10:52 am

Nonstop4h 52m

$194

SeattleChicago

SEA - ORD

SEAORD

Seattle/Tacoma Intl

Tue 12/16

5:50 pm-11:59 pm

Nonstop4h 09m

Chicago O'Hare Intl

Sat 1/17

6:50 pm-9:41 pm

Nonstop4h 51m

$194

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Sat 10/11

5:45 am-5:00 pm

1 stop9h 15m

Lambert-St Louis

Sat 10/18

3:35 pm-9:45 pm

1 stop8h 10m

$202

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Sat 11/15

6:00 am-5:23 pm

1 stop9h 23m

Lambert-St Louis

Mon 11/17

5:34 pm-11:59 pm

1 stop8h 25m

$203

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Thu 11/27

11:10 pm-9:46 am

1 stop8h 36m

Lambert-St Louis

Tue 12/2

5:34 pm-12:21 am

1 stop8h 47m

$203

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Fri 11/7

11:55 pm-8:51 am

1 stop6h 56m

Lambert-St Louis

Tue 11/11

6:50 am-12:56 pm

1 stop8h 06m

$203

SeattleChicago

SEA - ORD

SEAORD

Seattle/Tacoma Intl

Tue 1/6

5:20 am-1:16 pm

1 stop5h 56m

Chicago O'Hare Intl

Tue 1/20

6:50 pm-9:41 pm

Nonstop4h 51m

$204

SeattleChicago

SEA - ORD

SEAORD

Seattle/Tacoma Intl

Tue 10/7

1:57 pm-8:12 pm

Nonstop4h 15m

Chicago O'Hare Intl

Tue 10/14

4:10 pm-6:49 pm

Nonstop4h 39m

$209

SeattleChicago

SEA - ORD

SEAORD

Seattle/Tacoma Intl

Sat 1/10

11:45 am-5:50 pm

Nonstop4h 05m

Chicago O'Hare Intl

Wed 1/21

6:50 pm-9:41 pm

Nonstop4h 51m

$209

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Fri 11/7

11:55 pm-8:51 am

1 stop6h 56m

Lambert-St Louis

Mon 11/10

5:34 pm-11:59 pm

1 stop8h 25m

$209

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/17

Showing 1-10 of 60 results
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Best time to book a flight from Seattle to Illinois

Have a flexible travel schedule? Discover the best time to fly to Illinois from Seattle with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from Seattle to Illinois

What is the cheapest month to book a flight from Seattle to Illinois?

Currently, August is the cheapest month in which you can book a flight from Seattle to Illinois (average of $245). Flying from Seattle to Illinois in March is currently the most expensive (average of $321). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from SEA to IL?

Find hourly flight availability from Seattle to Illinois. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated September 17, 2025.

Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Seattle to Illinois as you normally would.

Weekly flight availability from Seattle to Illinois

Explore weekly flight availability from Seattle to Illinois. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated September 17, 2025.

The most flights from SEA to USIL are scheduled on a Monday (68 on average). You will have fewer flight options on Friday, which is when the least amount of flights are scheduled (53 on average).

Reviews of airlines servicing Illinois

Get insights into the airlines that provide service to Illinois. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Illinois. Reviews last updated September 17, 2025.
Read through reviews of airlines operating flights from Seattle to Illinois, such as Alaska Airlines, Southwest, and Delta. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.1

Overall

8.0

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.1

Overall

8.0

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
Southwest
8.0
Very good
4,242 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.1

Overall

8.0

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
Delta
8.0
Very good
7,961 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.1

Overall

8.0

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
United Airlines
7.4
Good
8,926 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.1

Overall

8.0

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
American Airlines
7.2
Good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.1

Overall

8.0

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.

Related info for your journey

Find useful and relevant information for your journey from Seattle to Illinois. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • What airport do you fly from for flights from Seattle to Illinois?

    Most people fly from Seattle/Tacoma Intl (SEA) if they book a flight from Seattle to Illinois. Seattle/Tacoma Intl is conveniently located just 11.4 mi from Seattle’s city center.

  • How long is the flight from Seattle to Illinois?

    Airlines like Alaska Airlines, Southwest, and Delta fly from Seattle to Illinois in about 4h 13m. The time it takes to get you to your destination can typically vary by up to 5h 10m. The distance between Seattle and Illinois is about 1715 mi. When browsing for deals, the options you’ll see will be for both nonstop flights and flights with stops.

  • What are the cheapest airlines to fly from Seattle to Illinois one-way?

    The cheapest airlines for a one-way flight from Seattle to Illinois are United Airlines ($94), Hawaiian Airlines ($99), and Delta ($99).

  • What are the most popular routes from Seattle to Illinois?

    The most popular flight routes from Seattle to Illinois are Seattle/Tacoma Intl - Chicago O'Hare Intl, Seattle/Tacoma Intl - Chicago Midway and Seattle/Tacoma Intl - Lambert-St Louis.

  • What are the most reliable airlines from Seattle to Illinois?

    No one likes to see their flight delayed. When booking a flight from Seattle to Illinois consider choosing WestJet (100%), KLM (100%) or Avianca (92%) as they are the most reliable in getting you off to your destination on time.

  • What are the cheapest flights from Seattle to Illinois?

    On average you can expect to pay $791 for a flight from Seattle to Illinois. The cheapest flight overall is $103 while the most popular route, (Seattle/Tacoma Intl - Chicago O'Hare Intl) is currently priced at $155.

  • Can I find deals for flights from Seattle to Illinois that include hotel bookings?

    Yes. In addition to deals on Seattle to Illinois flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Seattle to Illinois?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Seattle to Illinois.

  • Can I find deals for business class flights from Seattle to Illinois?

    Yes. Cheapflights offers flight deals from Seattle to Illinois by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from Seattle to Illinois?

    Currently, August is the cheapest month in which you can book a flight from Seattle to Illinois (average of $245). Flying from Seattle to Illinois in March is currently the most expensive (average of $321). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

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Alternative routes for Seattle to Illinois

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Top 8 airlines flying from Seattle to Illinois

Discover the top 8 airlines that operate flights from Seattle to Illinois. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated September 17, 2025.
AirlineCheapestAverageFlexibilityOn-time
Spirit AirlinesCheapest$107Average$189FlexibilityNo cancel feeOn-time65%
DeltaCheapest$119Average$292FlexibilityNo cancel feeOn-timeN/A
Hawaiian AirlinesCheapest$121Average$288FlexibilityNo cancel feeOn-time85%
FrontierCheapest$137Average$271FlexibilityNo cancel feeOn-time62%
United AirlinesCheapest$169Average$523FlexibilityNo cancel feeOn-time69%
Alaska AirlinesCheapest$171Average$478FlexibilityNo cancel feeOn-time75%
American AirlinesCheapest$177Average$447FlexibilityNo cancel feeOn-time71%
SouthwestCheapest$184Average$384FlexibilityNo cancel feeOn-time63%

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