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$80+ 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 10/8. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — ORD
Aug 23 — Aug 301
Sat 8/23
Sat 8/30
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 August 18, 2025.

Round-trip from

$169
(FlightHub)

One-way from

$80
(Priceline)

Popular in

December

Cheapest in

January

Average price

$287

Good round-trip deal

$266 or less

Good one-way deal

$161 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 ($16 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease ($8 potential savings vs. average RT price).
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Average for round-trip flights in August 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 August 18, 2025.

This FlightHub deal was found by Cheapflights users on 8/17. 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/246:39 pmSEA - STL
1 stop19h 17mFrontier
Sun 10/267:52 pmSTL - SEA
1 stop18h 15mFrontier
Deal found 8/17$169
This Southwest deal was found by Cheapflights users on 8/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/1611:10 pmSEA - STL
1 stop9h 05mSouthwest
Sun 9/2111:10 amSTL - SEA
Nonstop4h 20mSouthwest
Deal found 8/16$173
This FlightHub deal was found by Cheapflights users on 8/17. 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/256:12 amSEA - STL
1 stop24h 54mFrontier
Mon 10/67:55 pmSTL - SEA
1 stop18h 12mFrontier
Deal found 8/17$175
This Delta deal was found by Cheapflights users on 8/17. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/205:30 amSEA - STL
1 stop6h 14mDelta
Tue 9/302:15 pmSTL - SEA
1 stop9h 51mDelta
Deal found 8/17$177
This Southwest deal was found by Cheapflights users on 8/17. 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.
Tue 9/236:45 amSEA - STL
2 stops8h 55mSouthwest
Sun 9/2811:10 amSTL - SEA
Nonstop4h 20mSouthwest
Deal found 8/17$178
This Southwest deal was found by Cheapflights users on 8/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/512:05 pmSEA - STL
Nonstop4h 00mSouthwest
Mon 9/87:20 pmSTL - SEA
1 stop6h 45mSouthwest
Deal found 8/16$179
This Southwest deal was found by Cheapflights users on 8/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/96:45 amSEA - STL
2 stops8h 55mSouthwest
Sat 9/134:45 pmSTL - SEA
1 stop8h 45mSouthwest
Deal found 8/16$182
This Delta deal was found by Cheapflights users on 8/17. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/205:30 amSEA - STL
1 stop6h 14mDelta
Sun 10/55:40 pmSTL - SEA
1 stop8h 03mDelta
Deal found 8/17$183
This Expedia deal was found by Cheapflights users on 8/16. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/97:00 amSEA - ORD
1 stop12h 28mMultiple Airlines
Tue 9/236:20 amORD - SEA
Nonstop4h 32mMultiple Airlines
Deal found 8/16$186
This Kiwi.com deal was found by Cheapflights users on 8/16. 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.
Mon 9/2912:59 amSEA - ORD
Nonstop4h 04mHawaiian Airlines
Tue 10/78:20 amORD - SEA
1 stop8h 48mHawaiian Airlines
Deal found 8/16$187
This Kiwi.com deal was found by Cheapflights users on 8/17. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/133:59 pmSEA - ORD
Nonstop4h 08mHawaiian Airlines
Sat 9/205:45 pmORD - SEA
Nonstop4h 32mHawaiian Airlines
Deal found 8/17$188
This Hawaiian Airlines deal was found by Cheapflights users on 8/16. 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 Hawaiian Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/105:55 pmSEA - ORD
Nonstop4h 08mHawaiian Airlines
Sat 9/135:45 pmORD - SEA
Nonstop4h 32mHawaiian Airlines
Deal found 8/16$189

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 August 18, 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

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Mon 9/22

6:12 am-9:06 am

1 stop24h 54m

Lambert-St Louis

Fri 10/3

7:55 pm-12:30 am

1 stop6h 35m

$169

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Sat 9/20

7:00 am-9:06 am

1 stop24h 06m

Lambert-St Louis

Fri 9/26

7:55 pm-12:30 am

1 stop6h 35m

$169

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Fri 10/24

6:39 pm-3:56 pm

1 stop19h 17m

Lambert-St Louis

Tue 10/28

8:40 pm-12:13 pm

1 stop17h 33m

$169

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Mon 9/22

6:12 am-9:06 am

1 stop24h 54m

Lambert-St Louis

Thu 10/2

7:55 pm-12:30 am

1 stop6h 35m

$169

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Fri 10/24

6:39 pm-3:56 pm

1 stop19h 17m

Lambert-St Louis

Mon 10/27

7:52 pm-12:13 pm

1 stop18h 21m

$169

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Tue 9/23

7:00 am-9:06 am

1 stop24h 06m

Lambert-St Louis

Fri 10/3

7:55 pm-12:30 am

1 stop6h 35m

$169

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Tue 9/23

7:00 am-9:06 am

1 stop24h 06m

Lambert-St Louis

Thu 10/2

7:55 pm-12:30 am

1 stop6h 35m

$169

SeattleSt. Louis

SEA - STL

SEASTL

Seattle/Tacoma Intl

Wed 9/24

7:00 am-9:06 am

1 stop24h 06m

Lambert-St Louis

Mon 9/29

7:55 pm-12:30 am

1 stop6h 35m

$169

SeattleChicago

SEA - ORD

SEAORD

Seattle/Tacoma Intl

Fri 9/5

12:59 am-7:03 am

Nonstop4h 04m

Chicago O'Hare Intl

Tue 9/23

6:20 am-8:52 am

Nonstop4h 32m

$189

SeattleChicago

SEA - ORD

SEAORD

Seattle/Tacoma Intl

Sat 9/13

5:59 pm-11:59 pm

Nonstop4h 00m

Chicago O'Hare Intl

Wed 9/17

5:30 pm-8:08 pm

Nonstop4h 38m

$189

Flights are sorted by cheapest round-trip flights first.

Deals found on 8/16

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 August 18, 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 August 18, 2025.

The most flights from SEA to USIL are scheduled on a Sunday (83 on average). You will have fewer flight options on Wednesday, which is when the least amount of flights are scheduled (18 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 August 18, 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

Overall

8.0

Food

7.1

Crew

8.5

Entertainment

7.0

Boarding

8.1

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Food

7.1

Crew

8.5

Entertainment

7.0

Boarding

8.1

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Southwest
8.0
Very good
4,246 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Food

7.1

Crew

8.5

Entertainment

7.0

Boarding

8.1

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Delta
8.0
Very good
7,981 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Food

7.1

Crew

8.5

Entertainment

7.0

Boarding

8.1

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
United Airlines
7.4
Good
8,925 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Food

7.1

Crew

8.5

Entertainment

7.0

Boarding

8.1

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
American Airlines
7.2
Good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Food

7.1

Crew

8.5

Entertainment

7.0

Boarding

8.1

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.

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.

  • 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 Frontier ($80), United Airlines ($84), and Southwest ($85).

  • 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 Austrian Airlines (90%), WestJet (89%) or KLM (89%) 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 $779 for a flight from Seattle to Illinois. The cheapest flight overall is $93 while the most popular route, (Seattle/Tacoma Intl - Chicago O'Hare Intl) is currently priced at $176.

  • 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

See prices for flight routes from nearby airports that may be better suited for you.
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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 August 18, 2025.
AirlineCheapestAverageFlexibilityOn-time
Spirit AirlinesCheapest$93Average$189FlexibilityNo cancel feeOn-time65%
DeltaCheapest$117Average$286FlexibilityNo cancel feeOn-timeN/A
Hawaiian AirlinesCheapest$121Average$288FlexibilityNo cancel feeOn-time85%
FrontierCheapest$137Average$286FlexibilityNo cancel feeOn-time62%
United AirlinesCheapest$162Average$458FlexibilityNo cancel feeOn-time69%
Alaska AirlinesCheapest$169Average$473FlexibilityNo cancel feeOn-time75%
American AirlinesCheapest$169Average$455FlexibilityNo cancel feeOn-time71%
SouthwestCheapest$179Average$386FlexibilityNo cancel feeOn-time63%

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