$89+ 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 10/13. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — ORD
Aug 28 — Sep 41
Round-trip
1 adult, Economy
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Find cheap flights from Seattle to Illinois with Cheapflights
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Cheapest flights from Seattle to IllinoisExplore 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 July 29, 2026.
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 July 29, 2026.
This American Airlines deal was found by Cheapflights users on 7/28. 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.
Wed 9/161:40 pm
SEA
- PIA
1 stop8h 28m
American Airlines
Sat 9/195:28 pm
PIA
- SEA
1 stop8h 43m
American Airlines
Deal found 7/28![American Airlines logo]()
$281
This Southwest deal was found by Cheapflights users on 7/27. 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.
Mon 9/281:25 pm
SEA
- STL
2 stops9h 15m
Southwest
Thu 10/18:35 am
STL
- SEA
1 stop11h 35m
Southwest
Deal found 7/27![Southwest logo]()
$293
This Kiwi.com deal was found by Cheapflights users on 7/27. 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 8/168:53 pm
SEA
- STL
1 stop19h 22m
Frontier
Mon 8/247:58 pm
STL
- SEA
1 stop15h 21m
Frontier
Deal found 7/27![Frontier logo]()
$294
This Flightnetwork deal was found by Cheapflights users on 7/28. 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 Flightnetwork is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/129:45 pm
SEA
- ORD
1 stop29h 53m
Multiple Airlines
Tue 9/157:00 pm
ORD
- SEA
Nonstop4h 38m
Multiple Airlines
Deal found 7/28![Multiple Airlines logo]()
$295
This Kiwi.com deal was found by Cheapflights users on 7/27. 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.
Tue 10/64:27 pm
SEA
- STL
1 stop24h 50m
Frontier
Tue 10/2710:35 am
STL
- SEA
2 stops25h 16m
Frontier
Deal found 7/27![Frontier logo]()
$295
This Kiwi.com deal was found by Cheapflights users on 7/28. 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 8/1510:34 am
SEA
- ORD
1 stop17h 43m
Frontier
Sat 8/222:41 pm
ORD
- SEA
1 stop20h 38m
Frontier
Deal found 7/28![Frontier logo]()
$296
This Trip.com deal was found by Cheapflights users on 7/27. 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.
Tue 8/188:53 pm
SEA
- STL
1 stop18h 57m
Frontier
Thu 8/207:58 pm
STL
- SEA
1 stop15h 21m
Frontier
Deal found 7/27![Frontier logo]()
$296
This Trip.com deal was found by Cheapflights users on 7/29. 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.
Wed 8/198:53 pm
SEA
- ORD
1 stop20h 09m
Frontier
Sun 8/238:11 pm
ORD
- SEA
1 stop16h 28m
Frontier
Deal found 7/29![Frontier logo]()
$297
This Southwest deal was found by Cheapflights users on 7/28. 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 9/2512:05 pm
SEA
- STL
Nonstop4h 00m
Southwest
Sun 9/2710:55 am
STL
- SEA
Nonstop4h 20m
Southwest
Deal found 7/28![Southwest logo]()
$297
This CheapOair deal was found by Cheapflights users on 7/27. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/128:13 pm
SEA
- ORD
1 stop7h 24m
Frontier
Sun 8/167:29 am
ORD
- SEA
1 stop29h 35m
Frontier
Deal found 7/27![Frontier logo]()
$298
This CheapOair deal was found by Cheapflights users on 7/27. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/258:53 pm
SEA
- STL
1 stop18h 57m
Frontier
Sun 8/306:45 pm
STL
- SEA
1 stop17h 54m
Frontier
Deal found 7/27![Frontier logo]()
$298
This Frontier deal was found by Cheapflights users on 7/28. 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.
Fri 10/97:00 pm
SEA
- ORD
1 stop8h 42m
Frontier
Mon 10/126:50 am
ORD
- SEA
1 stop12h 55m
Frontier
Deal found 7/28![Frontier logo]()
$299
Best flights from Seattle to IllinoisDiscover carefully curated flight deals from Seattle to Illinois that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated July 29, 2026.
Discover carefully curated flight deals from Seattle to Illinois that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated July 29, 2026.
This American Airlines deal was found by Cheapflights users on 7/24. 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.
Wed 9/163:41 pm
SEA
- PIA
1 stop6h 27m
American Airlines
Tue 9/225:28 pm
PIA
- SEA
1 stop8h 43m
American Airlines
Deal found 7/24![American Airlines logo]()
$281
This Southwest deal was found by Cheapflights users on 7/28. 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 9/2512:05 pm
SEA
- STL
Nonstop4h 00m
Southwest
Sun 9/2710:55 am
STL
- SEA
Nonstop4h 20m
Southwest
Deal found 7/28![Southwest logo]()
$297
This Kiwi.com deal was found by Cheapflights users on 7/27. 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.
Wed 8/267:06 pm
SEA
- RFD
2 stops18h 03m
Multiple Airlines
Sun 8/309:35 pm
RFD
- SEA
1 stop15h 04m
Multiple Airlines
Deal found 7/27![Multiple Airlines logo]()
$299
This Alaska Airlines deal was found by Cheapflights users on 7/28. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/308:33 am
SEA
- ORD
Nonstop4h 21m
Alaska Airlines
Sat 10/39:00 am
ORD
- SEA
Nonstop4h 44m
Alaska Airlines
Deal found 7/28![Alaska Airlines logo]()
$317
This United Airlines deal was found by Cheapflights users on 7/29. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/291:16 pm
SEA
- ORD
1 stop7h 43m
United Airlines
Sat 9/57:00 am
ORD
- SEA
Nonstop4h 35m
United Airlines
Deal found 7/29![United Airlines logo]()
$327
This Delta deal was found by Cheapflights users on 7/24. 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.
Tue 9/2210:59 pm
SEA
- BMI
1 stop10h 19m
Delta
Mon 9/284:32 pm
BMI
- SEA
1 stop9h 26m
Delta
Deal found 7/24![Delta logo]()
$356
This American Airlines deal was found by Cheapflights users on 7/28. 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.
Wed 9/161:40 pm
SEA
- PIA
1 stop8h 28m
American Airlines
Sat 9/195:28 pm
PIA
- SEA
1 stop8h 43m
American Airlines
Deal found 7/28![American Airlines logo]()
$281
This Kiwi.com deal was found by Cheapflights users on 7/28. 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.
Wed 9/169:45 pm
SEA
- RFD
1 stop20h 54m
Multiple Airlines
Sun 9/209:29 pm
RFD
- SEA
1 stop14h 13m
Multiple Airlines
Deal found 7/28![Multiple Airlines logo]()
$307
This Southwest deal was found by Cheapflights users on 7/29. 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 8/295:30 pm
SEA
- MDW
1 stop9h 00m
Southwest
Sat 9/51:15 pm
MDW
- SEA
1 stop7h 45m
Southwest
Deal found 7/29![Southwest logo]()
$337
This United Airlines deal was found by Cheapflights users on 7/28. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/77:00 am
SEA
- ORD
Nonstop4h 15m
United Airlines
Sun 10/115:00 am
ORD
- SEA
1 stop7h 01m
United Airlines
Deal found 7/28![United Airlines logo]()
$357
This Delta deal was found by Cheapflights users on 7/27. 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.
Thu 9/310:50 am
SEA
- ORD
Nonstop4h 10m
Delta
Wed 9/97:00 am
ORD
- SEA
Nonstop4h 35m
Delta
Deal found 7/27![Delta logo]()
$357
This Alaska Airlines deal was found by Cheapflights users on 7/28. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/28:05 am
SEA
- STL
Nonstop3h 59m
Alaska Airlines
Sun 9/67:36 pm
STL
- SEA
Nonstop4h 23m
Alaska Airlines
Deal found 7/28![Alaska Airlines logo]()
$357
This Southwest deal was found by Cheapflights users on 7/27. 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 8/2511:05 pm
SEA
- MDW
Nonstop4h 00m
Southwest
Mon 8/319:20 pm
MDW
- SEA
Nonstop4h 35m
Southwest
Deal found 7/27![Southwest logo]()
$357
This American Airlines deal was found by Cheapflights users on 7/25. 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.
Fri 8/285:00 am
SEA
- PIA
1 stop8h 53m
American Airlines
Sun 8/304:43 pm
PIA
- SEA
1 stop10h 07m
American Airlines
Deal found 7/25![American Airlines logo]()
$359
This United Airlines deal was found by Cheapflights users on 7/29. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/1611:59 pm
SEA
- STL
1 stop8h 11m
United Airlines
Tue 9/221:36 pm
STL
- SEA
2 stops9h 07m
United Airlines
Deal found 7/29![United Airlines logo]()
$362
This Delta deal was found by Cheapflights users on 7/27. 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 10/1710:35 pm
SEA
- MLI
1 stop9h 47m
Delta
Tue 10/2011:08 am
MLI
- SEA
2 stops12h 57m
Delta
Deal found 7/27![Delta logo]()
$364
This Alaska Airlines deal was found by Cheapflights users on 7/25. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/227:04 am
SEA
- ORD
1 stop9h 49m
Alaska Airlines
Tue 10/273:49 pm
ORD
- SEA
Nonstop4h 39m
Alaska Airlines
Deal found 7/25![Alaska Airlines logo]()
$367
This Kiwi.com deal was found by Cheapflights users on 7/24. 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.
Wed 8/197:06 pm
SEA
- RFD
2 stops18h 03m
Multiple Airlines
Sun 8/239:35 pm
RFD
- SEA
1 stop15h 04m
Multiple Airlines
Deal found 7/24![Multiple Airlines logo]()
$376
This Southwest deal was found by Cheapflights users on 7/26. 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.
Wed 9/911:05 pm
SEA
- MDW
Nonstop4h 00m
Southwest
Wed 9/1610:35 am
MDW
- SEA
Nonstop4h 30m
Southwest
Deal found 7/26![Southwest logo]()
$357
This United Airlines deal was found by Cheapflights users on 7/28. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/29:05 am
SEA
- STL
2 stops9h 41m
United Airlines
Sun 9/63:13 pm
STL
- SEA
1 stop8h 23m
United Airlines
Deal found 7/28![United Airlines logo]()
$363
This Delta deal was found by Cheapflights users on 7/28. 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.
Fri 9/257:15 am
SEA
- ORD
Nonstop4h 14m
Delta
Mon 9/285:44 pm
ORD
- SEA
Nonstop4h 36m
Delta
Deal found 7/28![Delta logo]()
$367
This Alaska Airlines deal was found by Cheapflights users on 7/28. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/37:40 am
SEA
- ORD
1 stop9h 41m
Alaska Airlines
Mon 9/76:00 am
ORD
- SEA
Nonstop4h 30m
Alaska Airlines
Deal found 7/28![Alaska Airlines logo]()
$367
This Kiwi.com deal was found by Cheapflights users on 7/27. 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.
Thu 9/104:27 pm
SEA
- RFD
2 stops23h 44m
Multiple Airlines
Sun 9/139:29 pm
RFD
- SEA
1 stop14h 13m
Multiple Airlines
Deal found 7/27![Multiple Airlines logo]()
$378
This Southwest deal was found by Cheapflights users on 7/29. 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.
Thu 9/1012:35 pm
SEA
- MDW
2 stops8h 50m
Southwest
Sat 9/196:50 am
MDW
- SEA
1 stop8h 20m
Southwest
Deal found 7/29![Southwest logo]()
$362
This Alaska Airlines deal was found by Cheapflights users on 7/27. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/255:51 pm
SEA
- ORD
Nonstop4h 08m
Alaska Airlines
Wed 8/262:18 pm
ORD
- SEA
1 stop9h 22m
Alaska Airlines
Deal found 7/27![Alaska Airlines logo]()
$367
This United Airlines deal was found by Cheapflights users on 7/27. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/185:13 pm
SEA
- ORD
Nonstop4h 04m
United Airlines
Mon 9/217:00 am
ORD
- SEA
Nonstop4h 36m
United Airlines
Deal found 7/27![United Airlines logo]()
$373
This Delta deal was found by Cheapflights users on 7/25. 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 8/2611:59 pm
SEA
- MLI
1 stop8h 26m
Delta
Sat 8/2911:08 am
MLI
- SEA
2 stops12h 57m
Delta
Deal found 7/25![Delta logo]()
$374
This Alaska Airlines deal was found by Cheapflights users on 7/28. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/275:51 pm
SEA
- ORD
Nonstop4h 08m
Alaska Airlines
Sun 8/306:00 am
ORD
- SEA
Nonstop4h 30m
Alaska Airlines
Deal found 7/28![Alaska Airlines logo]()
$367
This Southwest deal was found by Cheapflights users on 7/27. 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.
Wed 8/1911:05 pm
SEA
- MDW
Nonstop4h 00m
Southwest
Sat 8/2212:40 pm
MDW
- SEA
1 stop8h 50m
Southwest
Deal found 7/27![Southwest logo]()
$367
This American Airlines deal was found by Cheapflights users on 7/29. 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.
Thu 10/1512:04 pm
SEA
- MLI
1 stop9h 13m
American Airlines
Sun 10/187:00 am
MLI
- SEA
1 stop8h 36m
American Airlines
Deal found 7/29![American Airlines logo]()
$452
Last-minute flights from Seattle to IllinoisDiscover last-minute flight deals from Seattle to Illinois. Data last updated July 29, 2026 and is based on user searches.
Discover last-minute flight deals from Seattle to Illinois. Data last updated July 29, 2026 and is based on user searches.
This CheapOair deal was found by Cheapflights users on 7/27. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/128:13 pm
SEA
- ORD
1 stop7h 24m
Frontier
Sun 8/167:29 am
ORD
- SEA
1 stop29h 35m
Frontier
Deal found 7/27![Frontier logo]()
$298
This Kiwi.com deal was found by Cheapflights users on 7/25. 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.
Wed 8/128:13 pm
SEA
- ORD
1 stop7h 24m
Frontier
Thu 8/202:41 pm
ORD
- SEA
1 stop20h 38m
Frontier
Deal found 7/25![Frontier logo]()
$299
This Kiwi.com deal was found by Cheapflights users on 7/28. 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 8/1510:34 am
SEA
- ORD
1 stop17h 43m
Frontier
Sat 8/222:41 pm
ORD
- SEA
1 stop20h 38m
Frontier
Deal found 7/28![Frontier logo]()
$296
This Kiwi.com deal was found by Cheapflights users on 7/27. 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 8/168:53 pm
SEA
- STL
1 stop19h 22m
Frontier
Mon 8/247:58 pm
STL
- SEA
1 stop15h 21m
Frontier
Deal found 7/27![Frontier logo]()
$294
This Trip.com deal was found by Cheapflights users on 7/27. 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.
Tue 8/188:53 pm
SEA
- STL
1 stop18h 57m
Frontier
Thu 8/207:58 pm
STL
- SEA
1 stop15h 21m
Frontier
Deal found 7/27![Frontier logo]()
$296
This Trip.com deal was found by Cheapflights users on 7/29. 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.
Wed 8/198:53 pm
SEA
- ORD
1 stop20h 09m
Frontier
Sun 8/238:11 pm
ORD
- SEA
1 stop16h 28m
Frontier
Deal found 7/29![Frontier logo]()
$297
This Trip.com deal was found by Cheapflights users on 7/27. 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.
Thu 8/202:37 pm
SEA
- ORD
1 stop20h 59m
Frontier
Wed 8/262:41 pm
ORD
- SEA
1 stop24h 41m
Frontier
Deal found 7/27![Frontier logo]()
$301
This Trip.com deal was found by Cheapflights users on 7/28. 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.
Tue 8/2510:34 am
SEA
- ORD
1 stop17h 43m
Multiple Airlines
Tue 9/13:43 pm
ORD
- SEA
Nonstop4h 33m
Multiple Airlines
Deal found 7/28![Multiple Airlines logo]()
$295
This CheapOair deal was found by Cheapflights users on 7/27. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/258:53 pm
SEA
- STL
1 stop18h 57m
Frontier
Sun 8/306:45 pm
STL
- SEA
1 stop17h 54m
Frontier
Deal found 7/27![Frontier logo]()
$298
This Kiwi.com deal was found by Cheapflights users on 7/27. 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.
Wed 8/267:06 pm
SEA
- RFD
2 stops18h 03m
Multiple Airlines
Sun 8/309:35 pm
RFD
- SEA
1 stop15h 04m
Multiple Airlines
Deal found 7/27![Multiple Airlines logo]()
$299
This Booking.com deal was found by Cheapflights users on 7/28. 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.
Wed 8/2610:34 am
SEA
- ORD
1 stop17h 25m
Multiple Airlines
Wed 9/26:54 pm
ORD
- SEA
Nonstop4h 49m
Multiple Airlines
Deal found 7/28![Multiple Airlines logo]()
$300
This Gotogate deal was found by Cheapflights users on 7/28. 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 Gotogate is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/2910:34 am
SEA
- ORD
1 stop17h 25m
Multiple Airlines
Sat 9/59:00 am
ORD
- SEA
Nonstop4h 39m
Multiple Airlines
Deal found 7/28![Multiple Airlines logo]()
$302
One-way flights from Seattle to IllinoisSearch for one-way flight options from Seattle to Illinois. Find affordable one-way fares based on user searches. Data last updated July 29, 2026.
Search for one-way flight options from Seattle to Illinois. Find affordable one-way fares based on user searches. Data last updated July 29, 2026.
This Southwest deal was found by Cheapflights users on 7/28. 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 8/2811:00 pm
SEA
- STL
1 stop7h 15m
Southwest
Deal found 7/28![Southwest logo]()
$89
This Delta deal was found by Cheapflights users on 7/28. 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.
Thu 8/2711:59 pm
SEA
- STL
1 stop6h 38m
Delta
Deal found 7/28![Delta logo]()
$94
This Southwest deal was found by Cheapflights users on 7/28. 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 10/2712:05 pm
SEA
- STL
2 stops8h 00m
Southwest
Deal found 7/28![Southwest logo]()
$99
This Kiwi.com deal was found by Cheapflights users on 7/25. 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.
Wed 8/267:06 pm
SEA
- STL
1 stop22h 07m
Frontier
Deal found 7/25![Frontier logo]()
$103
This Delta deal was found by Cheapflights users on 7/28. 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.
Fri 8/2811:05 am
SEA
- STL
1 stop5h 50m
Delta
Deal found 7/28![Delta logo]()
$104
This Southwest deal was found by Cheapflights users on 7/26. 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 9/255:00 am
SEA
- STL
2 stops10h 55m
Southwest
Deal found 7/26![Southwest logo]()
$109
This Trip.com deal was found by Cheapflights users on 7/28. 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.
Wed 8/197:06 pm
SEA
- STL
1 stop22h 07m
Frontier
Deal found 7/28![Frontier logo]()
$125
This Kiwi.com deal was found by Cheapflights users on 7/28. 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 8/302:37 pm
SEA
- STL
1 stop26h 36m
Frontier
Deal found 7/28![Frontier logo]()
$126
This Kiwi.com deal was found by Cheapflights users on 7/27. 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.
Wed 10/149:16 pm
SEA
- STL
2 stops19h 59m
Frontier
Deal found 7/27![Frontier logo]()
$133
This United Airlines deal was found by Cheapflights users on 7/25. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/259:05 am
SEA
- STL
2 stops9h 41m
United Airlines
Deal found 7/25![United Airlines logo]()
$134
This Trip.com deal was found by Cheapflights users on 7/27. 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.
Wed 8/128:13 pm
SEA
- ORD
1 stop7h 24m
Frontier
Deal found 7/27![Frontier logo]()
$148
This Kiwi.com deal was found by Cheapflights users on 7/27. 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.
Thu 8/2710:34 am
SEA
- ORD
1 stop17h 25m
Frontier
Deal found 7/27![Frontier logo]()
$149
Find flight deals from Seattle to Illinois
Keep the following information in mind while searching for Seattle to Illinois flight deals. Data was last updated July 29, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $281 (American Airlines) |
One-way from | $89 (Southwest) |
Popular in | June |
Cheapest in | February |
Average price | $397 |
Good round-trip deal | $384 or less |
Good one-way deal | $208 or less |
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 July 29, 2026.
Use the filters below to find and compare flights from Seattle to Illinois that are best for you.
Fly from
Fly to
Route
Depart
Return
Cheapest round-trip
SeattlePeoria
SEA - PIA
SEAPIA
Seattle/Tacoma Intl
Wed 9/16
3:41 pm-12:08 am
1 stop6h 27m
Greater Peoria
Tue 9/22
5:28 pm-12:11 am
1 stop8h 43m
$281
SeattlePeoria
SEA - PIA
SEAPIA
Seattle/Tacoma Intl
Wed 9/16
1:40 pm-12:08 am
1 stop8h 28m
Greater Peoria
Sat 9/19
5:28 pm-12:11 am
1 stop8h 43m
$281
Quickest round-trip
SeattleSt. Louis
SEA - STL
SEASTL
Seattle/Tacoma Intl
Fri 9/25
12:05 pm-6:05 pm
Nonstop4h 00m
Lambert-St Louis
Sun 9/27
10:55 am-1:15 pm
Nonstop4h 20m
$297
SeattleChicago
SEA - RFD
SEARFD
Seattle/Tacoma Intl
Wed 8/26
7:06 pm-3:09 pm
2 stops18h 03m
Chicago Greater Rockford
Sun 8/30
9:35 pm-10:39 am
1 stop15h 04m
$299
SeattleChicago
SEA - RFD
SEARFD
Seattle/Tacoma Intl
Wed 9/16
9:45 pm-8:39 pm
1 stop20h 54m
Chicago Greater Rockford
Sun 9/20
9:29 pm-9:42 am
1 stop14h 13m
$307
SeattleChicago
SEA - ORD
SEAORD
Seattle/Tacoma Intl
Wed 9/30
8:33 am-2:54 pm
Nonstop4h 21m
Chicago O'Hare Intl
Sat 10/3
9:00 am-11:44 am
Nonstop4h 44m
$317
SeattleChicago
SEA - ORD
SEAORD
Seattle/Tacoma Intl
Sat 8/29
1:16 pm-10:59 pm
1 stop7h 43m
Chicago O'Hare Intl
Sat 9/5
7:00 am-9:35 am
Nonstop4h 35m
$327
SeattleChicago
SEA - MDW
SEAMDW
Seattle/Tacoma Intl
Sat 8/29
5:30 pm-4:30 am
1 stop9h 00m
Chicago Midway
Sat 9/5
1:15 pm-7:00 pm
1 stop7h 45m
$337
SeattleBloomington
SEA - BMI
SEABMI
Seattle/Tacoma Intl
Tue 9/22
10:59 pm-11:18 am
1 stop10h 19m
Bloomington-Normal
Mon 9/28
4:32 pm-11:58 pm
1 stop9h 26m
$356
SeattleChicago
SEA - ORD
SEAORD
Seattle/Tacoma Intl
Wed 10/7
7:00 am-1:15 pm
Nonstop4h 15m
Chicago O'Hare Intl
Sun 10/11
5:00 am-10:01 am
1 stop7h 01m
$357
Showing 1-10 of 60 resultsSorted by cheapest first
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.
SEA-PIA
SEA-STL
SEA-RFD
SEA-ORD
SEA-BMI
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
SEA-USIL
SEA-PIA
SEA-STL
SEA-RFD
SEA-ORD
What is the cheapest month to book a flight from Seattle to Illinois?
Currently, February is the cheapest month in which you can book a flight from Seattle to Illinois (average of $262). Flying from Seattle to Illinois in June is currently the most expensive (average of $418). 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 July 29, 2026.
It’s typically best to fly out from Seattle to Illinois at noon. Doing so could potentially save you 6% on the flight price compared to flying in the morning, which is usually more expensive.
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 July 29, 2026.
The most flights from SEA to USIL are scheduled on a Monday (61 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (32 on average).
How much does it cost to fly round-trip from Seattle to Illinois?
Airfare is below average for this route at the moment.
Seattle to Illinois flights typically cost between $296 and $469 in September.The cheapest round-trip price found within the last 5 days was $295 on Multiple Airlines (Sep 12-Sep 15).
How far ahead should I book a flight from Seattle to Illinois?
The price you pay for your flight from Seattle to Illinois may vary depending on when you book. For the best chance of a lower fare, look to book 60 days in advance of your trip. Fares are likely to increase a fortnight or so before your departure date.
What is the cheapest day to fly from Seattle to Illinois?
Use this chart to determine the cheapest time to fly round-trip from Seattle to Illinois. Price data was last updated on July 25, 2026.
Travelers seeking maximum savings on their Seattle to Illinois flight should consider departing on Tuesday at noon when fares are most often at their lowest. Sunday at noon flights should be avoided if possible as fares are typically the most expensive at this time.
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 July 29, 2026.
Read through reviews of airlines operating flights from Seattle to Illinois, such as Southwest,Alaska Airlines, andDelta. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Crew
8.6
Overall
8.0
Boarding
8.1
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Crew
8.6
Overall
8.0
Boarding
8.1
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Crew
8.6
Overall
8.0
Boarding
8.1
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Crew
8.6
Overall
8.0
Boarding
8.1
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Crew
8.6
Overall
8.0
Boarding
8.1
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Crew
8.6
Overall
8.0
Boarding
8.1
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
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.
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Alternative routes for Seattle to Illinois
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Complete your trip
Complete your trip to Illinois by adding a car rental and/or hotel reservation to your travel itinerary.
Search flights from Seattle to Illinois by cabin class
Find flights from Seattle to Illinois, based on your preferred cabin class, be it economy, premium economy, business, or first class.
Seattle and Illinois flights
Browse other Seattle and Illinois flight options. Last updated on July 29, 2026.
Popular flight searches
Check out other popular destinations found by fellow travelers in 2026
Seattle to Illinois flights
Consider these flights traveling from Seattle to Illinois.
Top 7 airlines flying from Seattle to Illinois
Discover the top 7 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 July 29, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$118 | Average$219 | FlexibilityNo cancel fee | On-time85% | |
| Cheapest$133 | Average$355 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$177 | Average$363 | FlexibilityNo cancel fee | On-time75% | |
| Cheapest$182 | Average$441 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$182 | Average$433 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$193 | Average$310 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$239 | Average$378 | FlexibilityNo cancel fee | On-time63% |