$109+ Cheap flights from Ontario to Seattle (ONT - SEA)
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 8/4. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — SEA
Jul 28 — Aug 41
Round-trip
1 adult, Economy
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Find cheap flights from Ontario to Seattle with Cheapflights
1. Tell us where you want to go
Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”2. Select your favorite providers
We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.3. Compare prices and book
Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.Cheapflights Tip: The best prices from Ontario to Seattle/Tacoma Intl are usually found in January or October, booked 49 days in advance, depart on a Saturday or Friday and return on a Thursday
Cheap flight deals from Ontario to Seattle
Cheapest
Best
Last-minute
One-way
Cheapest flights from Ontario to SeattleExplore the most affordable flight options available from Ontario to Seattle. Find the lowest fares from popular airlines and budget airlines, with prices last updated on June 28, 2026.
Explore the most affordable flight options available from Ontario to Seattle. Find the lowest fares from popular airlines and budget airlines, with prices last updated on June 28, 2026.
This Kiwi.com deal was found by Cheapflights users on 6/23. 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 8/235:17 pm
ONT
- SEA
Nonstop2h 45m
Frontier
Sun 8/3011:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/23![Frontier logo]()
$194
This Frontier deal was found by Cheapflights users on 6/25. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/35:17 pm
ONT
- SEA
Nonstop2h 45m
Frontier
Sun 9/611:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/25![Frontier logo]()
$198
This Super.com deal was found by Cheapflights users on 6/23. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 8/174:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Thu 8/2011:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/23![Frontier logo]()
$199
This Booking.com deal was found by Cheapflights users on 6/26. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/43:40 pm
ONT
- SEA
1 stop19h 24m
Frontier
Wed 8/1911:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/26![Frontier logo]()
$201
This Frontier deal was found by Cheapflights users on 6/27. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/184:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Mon 8/2411:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/27![Frontier logo]()
$202
This Frontier deal was found by Cheapflights users on 6/25. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/224:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Sat 8/298:53 pm
SEA
- ONT
1 stop11h 10m
Frontier
Deal found 6/25![Frontier logo]()
$203
This Frontier deal was found by Cheapflights users on 6/23. 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.
Thu 9/35:17 pm
ONT
- SEA
Nonstop2h 45m
Frontier
Wed 9/97:00 am
SEA
- ONT
1 stop6h 57m
Frontier
Deal found 6/23![Frontier logo]()
$204
This Frontier deal was found by Cheapflights users on 6/27. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/224:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Mon 8/247:06 pm
SEA
- ONT
1 stop14h 58m
Frontier
Deal found 6/27![Frontier logo]()
$205
This Kiwi.com deal was found by Cheapflights users on 6/24. 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.
Sat 9/192:55 pm
ONT
- SEA
1 stop9h 32m
Frontier
Thu 9/2411:15 am
SEA
- ONT
Nonstop2h 48m
Frontier
Deal found 6/24![Frontier logo]()
$206
This Super.com deal was found by Cheapflights users on 6/24. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/266:00 am
ONT
- SEA
1 stop27h 19m
Frontier
Sun 8/3011:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/24![Frontier logo]()
$207
This Frontier deal was found by Cheapflights users on 6/24. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/74:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Wed 8/1911:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/24![Frontier logo]()
$208
Best flights from Ontario to SeattleDiscover carefully curated flight deals from Ontario to Seattle that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated June 28, 2026.
Discover carefully curated flight deals from Ontario to Seattle that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated June 28, 2026.
This Delta deal was found by Cheapflights users on 6/27. 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 8/223:35 pm
ONT
- SEA
Nonstop2h 52m
Delta
Mon 8/247:50 pm
SEA
- ONT
Nonstop2h 55m
Delta
Deal found 6/27![Delta logo]()
$247
This Alaska Airlines deal was found by Cheapflights users on 6/23. 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.
Sat 8/227:12 am
ONT
- SEA
1 stop6h 33m
Alaska Airlines
Mon 8/3110:41 am
SEA
- ONT
1 stop5h 06m
Alaska Airlines
Deal found 6/23![Alaska Airlines logo]()
$277
This Southwest deal was found by Cheapflights users on 6/26. 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 8/191:10 pm
ONT
- SEA
2 stops7h 05m
Southwest
Sat 8/221:50 pm
SEA
- ONT
2 stops6h 15m
Southwest
Deal found 6/26![Southwest logo]()
$312
This Alaska Airlines deal was found by Cheapflights users on 6/23. 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 9/14:27 pm
ONT
- SEA
2 stops6h 12m
Alaska Airlines
Sun 9/610:41 am
SEA
- ONT
1 stop5h 06m
Alaska Airlines
Deal found 6/23![Alaska Airlines logo]()
$335
This Southwest deal was found by Cheapflights users on 6/27. 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 8/121:10 pm
ONT
- SEA
2 stops7h 05m
Southwest
Wed 8/1912:40 pm
SEA
- ONT
2 stops7h 25m
Southwest
Deal found 6/27![Southwest logo]()
$342
This Delta deal was found by Cheapflights users on 6/24. 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.
Fri 8/75:05 pm
ONT
- SEA
1 stop5h 00m
Delta
Tue 8/117:15 am
SEA
- ONT
1 stop5h 01m
Delta
Deal found 6/24![Delta logo]()
$347
This Delta deal was found by Cheapflights users on 6/24. 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 7/215:10 pm
ONT
- SEA
1 stop4h 50m
Delta
Wed 7/297:15 am
SEA
- ONT
1 stop4h 55m
Delta
Deal found 6/24![Delta logo]()
$347
This Southwest deal was found by Cheapflights users on 6/23. 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 8/1412:35 pm
ONT
- SEA
2 stops8h 40m
Southwest
Mon 8/1711:50 am
SEA
- ONT
1 stop6h 10m
Southwest
Deal found 6/23![Southwest logo]()
$352
This Delta deal was found by Cheapflights users on 6/23. 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 8/16:01 pm
ONT
- SEA
Nonstop2h 49m
Delta
Mon 8/37:50 pm
SEA
- ONT
Nonstop2h 55m
Delta
Deal found 6/23![Delta logo]()
$353
This Southwest deal was found by Cheapflights users on 6/24. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/275:40 am
ONT
- SEA
2 stops6h 10m
Southwest
Sun 8/308:40 am
SEA
- ONT
1 stop4h 45m
Southwest
Deal found 6/24![Southwest logo]()
$377
Last-minute flights from Ontario to SeattleDiscover last-minute flight deals from Ontario to Seattle. Data last updated June 28, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Seattle. Data last updated June 28, 2026 and is based on user searches.
This Kiwi.com deal was found by Cheapflights users on 6/25. 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 7/154:09 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Wed 7/2211:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/25![Frontier logo]()
$229
This Super.com deal was found by Cheapflights users on 6/24. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 7/184:09 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Thu 7/2311:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/24![Frontier logo]()
$234
This Expedia deal was found by Cheapflights users on 6/26. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/223:40 pm
ONT
- SEA
1 stop18h 59m
Frontier
Tue 7/287:06 pm
SEA
- ONT
1 stop28h 44m
Frontier
Deal found 6/26![Frontier logo]()
$230
This Kiwi.com deal was found by Cheapflights users on 6/28. 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 7/254:09 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Tue 7/2811:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/28![Frontier logo]()
$231
This Super.com deal was found by Cheapflights users on 6/24. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 7/264:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Thu 8/2711:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/24![Frontier logo]()
$215
This Expedia deal was found by Cheapflights users on 6/24. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/281:38 pm
ONT
- SEA
1 stop21h 01m
Frontier
Tue 8/48:13 pm
SEA
- ONT
1 stop11h 50m
Frontier
Deal found 6/24![Frontier logo]()
$220
This Super.com deal was found by Cheapflights users on 6/24. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/284:09 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Wed 8/58:13 pm
SEA
- ONT
1 stop11h 50m
Frontier
Deal found 6/24![Frontier logo]()
$226
This Kiwi.com deal was found by Cheapflights users on 6/25. 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.
Fri 7/314:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Sun 8/3011:54 am
SEA
- ONT
Nonstop2h 51m
Frontier
Deal found 6/25![Frontier logo]()
$210
This Frontier deal was found by Cheapflights users on 6/24. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 7/314:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Wed 8/122:22 pm
SEA
- ONT
1 stop9h 28m
Frontier
Deal found 6/24![Frontier logo]()
$224
One-way flights from Ontario to SeattleSearch for one-way flight options from Ontario to Seattle. Find affordable one-way fares based on user searches. Data last updated June 28, 2026.
Search for one-way flight options from Ontario to Seattle. Find affordable one-way fares based on user searches. Data last updated June 28, 2026.
This Super.com deal was found by Cheapflights users on 6/24. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/43:40 pm
ONT
- SEA
1 stop19h 24m
Frontier
Deal found 6/24![Frontier logo]()
$109
This Expedia deal was found by Cheapflights users on 6/24. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/222:55 pm
ONT
- SEA
1 stop9h 32m
Frontier
Deal found 6/24![Frontier logo]()
$111
This Frontier deal was found by Cheapflights users on 6/26. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/197:56 pm
ONT
- SEA
1 stop13h 23m
Frontier
Deal found 6/26![Frontier logo]()
$112
This Jetabroad deal was found by Cheapflights users on 6/26. 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 Jetabroad is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/13:40 pm
ONT
- SEA
1 stop18h 59m
Frontier
Deal found 6/26![Frontier logo]()
$114
This Kiwi.com deal was found by Cheapflights users on 6/23. 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 7/164:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Deal found 6/23![Frontier logo]()
$115
This Kiwi.com deal was found by Cheapflights users on 6/23. 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 7/184:09 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Deal found 6/23![Frontier logo]()
$116
This Super.com deal was found by Cheapflights users on 6/24. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/284:09 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Deal found 6/24![Frontier logo]()
$117
This Super.com deal was found by Cheapflights users on 6/24. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/221:38 pm
ONT
- SEA
1 stop21h 01m
Frontier
Deal found 6/24![Frontier logo]()
$119
This Frontier deal was found by Cheapflights users on 6/23. 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.
Tue 8/114:09 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Deal found 6/23![Frontier logo]()
$120
This CheapOair deal was found by Cheapflights users on 6/27. 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.
Thu 7/234:49 pm
ONT
- SEA
Nonstop2h 49m
Frontier
Deal found 6/27![Frontier logo]()
$124
Find flight deals from Ontario to Seattle
Discover tips and strategies to find the most affordable flight options for your journey from Ontario (ONT) to Seattle (SEA). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated June 28, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $196 (Kiwi.com) |
One-way from | $109 (Super.com) |
Popular in | June |
Cheapest in | January |
Average price | $316 |
Good round-trip deal | $279 or less |
Good one-way deal | $189 or less |
Cheapflights Fare Finder
Customize your flight search to find flights from Ontario to Seattle 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 June 28, 2026.
Use the filters below to find and compare flights from Ontario to Seattle that are best for you.
Fly from
Fly to
Route
Depart
Return
Cheapest round-trip
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Sat 8/22
3:35 pm-6:27 pm
Nonstop2h 52m
Seattle/Tacoma Intl
Mon 8/24
7:50 pm-10:45 pm
Nonstop2h 55m
$247
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Sat 8/22
7:12 am-1:45 pm
1 stop6h 33m
Seattle/Tacoma Intl
Mon 8/31
10:41 am-3:47 pm
1 stop5h 06m
$277
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Wed 8/19
1:10 pm-8:15 pm
2 stops7h 05m
Seattle/Tacoma Intl
Sat 8/22
1:50 pm-8:05 pm
2 stops6h 15m
$312
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Tue 9/1
4:27 pm-10:39 pm
2 stops6h 12m
Seattle/Tacoma Intl
Sun 9/6
10:41 am-3:47 pm
1 stop5h 06m
$335
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Wed 8/12
1:10 pm-8:15 pm
2 stops7h 05m
Seattle/Tacoma Intl
Wed 8/19
12:40 pm-8:05 pm
2 stops7h 25m
$342
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Fri 8/7
5:05 pm-10:05 pm
1 stop5h 00m
Seattle/Tacoma Intl
Tue 8/11
7:15 am-12:16 pm
1 stop5h 01m
$347
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Tue 7/21
5:10 pm-10:00 pm
1 stop4h 50m
Seattle/Tacoma Intl
Wed 7/29
7:15 am-12:10 pm
1 stop4h 55m
$347
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Fri 8/14
12:35 pm-9:15 pm
2 stops8h 40m
Seattle/Tacoma Intl
Mon 8/17
11:50 am-6:00 pm
1 stop6h 10m
$352
Quickest round-trip
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Sat 8/1
6:01 pm-8:50 pm
Nonstop2h 49m
Seattle/Tacoma Intl
Mon 8/3
7:50 pm-10:45 pm
Nonstop2h 55m
$353
OntarioSeattle
ONT - SEA
ONTSEA
Ontario
Thu 8/27
5:40 am-11:50 am
2 stops6h 10m
Seattle/Tacoma Intl
Sun 8/30
8:40 am-1:25 pm
1 stop4h 45m
$377
Showing 1-10 of 21 resultsSorted by cheapest first
Compare providers for flights from Ontario to Seattle
Provider information is updated monthly. Please note that these providers often have deals for this flight, but the availability may vary on a day-by-day basis on Cheapflights.
Use the table below to compare price accuracy, trust ratings, and cancellation policies for each provider offering flight deals from Ontario to Seattle in June.
| Provider | Price Accuracy | Trust Score* |
|---|---|---|
| Price Accuracy1 star | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy2 stars | Trust Score*3 stars | |
| Price Accuracy1 star | Trust Score*3 stars | |
| Price Accuracy2 stars | Trust Score*1 star | |
| Price Accuracy- | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy2 stars | Trust Score*3 stars |
- Most accurate provider: When it comes to deals on Ontario-Seattle flights, users find the pricing of FlightHub to be most consistent on Cheapflights vs. FlightHub Users can find the same prices on Ontario-Seattle flight deals on Cheapflights vs. FlightHub >95% of the time. Price accuracy is based on data collected from Ontario-Seattle flight searches over the past month and is updated monthly.
- Most trusted provider: When it comes to deals on Ontario-Seattle flights, Cheapflights users trust FlightHub the most. FlightHub has received a user feedback score of 3 out of 3 stars (3 being the best), meaning they have been trusted the most by Cheapflights users looking for Ontario-Seattle flight deals. Provider user feedback score is based on Cheapflights searches over the past month and is updated monthly.
Best time to book a flight from Ontario to Seattle
Have a flexible travel schedule? Discover the best time to fly to Seattle from Ontario with our price prediction graph.
ONT-SEA
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 Ontario to Seattle
Prices
Airlines
Delays
How far ahead should I book a flight from Ontario to Seattle?
To ensure you get the cheapest price possible for a flight from Ontario to Seattle, you should look to book at least 48 days in advance of your intended travel date. The price of your flight may increase if you delay and leave booking until a week or so before departure.
What is the cheapest month to book a flight from Ontario to Seattle?
Currently, January is the cheapest month in which you can book a flight from Ontario to Seattle (average of $197). Flying from Ontario to Seattle in June is currently the most expensive (average of $305). 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 ONT to SEA?
Find hourly flight availability from Ontario to Seattle. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated June 28, 2026.
It’s typically best to fly out from Ontario to Seattle in the afternoon. Doing so could potentially save you 13% on the flight price compared to flying at noon, which is usually more expensive.
What is the cheapest day to fly from Ontario to Seattle?
Use this chart to determine the cheapest time to fly round-trip from Ontario to Seattle. Price data was last updated on June 27, 2026.
Travelers seeking maximum savings on their Ontario to Seattle flight should consider departing on Sunday afternoons when fares are most often at their lowest. Wednesday at noon flights should be avoided if possible as fares are typically the most expensive at this time.
How often are flights from Ontario to Seattle delayed?
About 8% of weekly flights between Ontario and Seattle have experienced delays in the past year, with the average delay time being 132 minutes.
What is the most punctual flight time for Ontario to Seattle flights?
Historically, flights departing in the morning are less likely to be delayed, whereas flights leaving in the evening tend to experience delays more often.
What day of the week experiences the fewest flight delays on this route?
Sunday tends to have the lowest number of delays on this route, whereas Thursday has historically faced a higher average of delays compared to other days of the week.
Which airline has the best punctuality record on Ontario to Seattle flights?
Over the last year, Delta have had the lowest number of delays on this route, with just 4% of flights being delayed.
The best insider tips for Ontario to Seattle flights
AI-powered summary based on content written by travel experts. AI can make mistakes.
Cheapflights partnered with top experts to bring you the best recommendations for your Ontario to Seattle trip
Our travel experts
Reviews of airlines servicing Seattle
Get insights into the airlines that provide service to Seattle. 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 Seattle. Reviews last updated June 28, 2026.
See what other customers who have flown with Alaska Airlines,Southwest, andDelta from Ontario to Seattle have to say. You can also see how each airline compares in terms of entertainment options, comfort, food, crew/service, and boarding process.
Entertainment
7.0
Boarding
8.1
Comfort
7.8
Food
7.0
Overall
7.9
Crew
8.5
Reviews
1 / 20
10.0
ExcellentAnonymous,Dec 2025
SJC - SEA
Entertainment
7.0
Boarding
8.1
Comfort
7.8
Food
7.0
Overall
7.9
Crew
8.5
Reviews
1 / 20
10.0
ExcellentAnonymous,Dec 2025
SJC - SEA
Entertainment
7.0
Boarding
8.1
Comfort
7.8
Food
7.0
Overall
7.9
Crew
8.5
Reviews
1 / 20
10.0
ExcellentAnonymous,Dec 2025
SJC - SEA
Entertainment
7.0
Boarding
8.1
Comfort
7.8
Food
7.0
Overall
7.9
Crew
8.5
Reviews
1 / 20
10.0
ExcellentAnonymous,Dec 2025
SJC - SEA
Entertainment
7.0
Boarding
8.1
Comfort
7.8
Food
7.0
Overall
7.9
Crew
8.5
Reviews
1 / 20
10.0
ExcellentAnonymous,Dec 2025
SJC - SEA
Entertainment
7.0
Boarding
8.1
Comfort
7.8
Food
7.0
Overall
7.9
Crew
8.5
Reviews
1 / 20
10.0
ExcellentAnonymous,Dec 2025
SJC - SEA
Related info for your journey
Find useful and relevant information for your journey from Ontario to Seattle. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.
Traveling to a place near Seattle?
Book flights to Seattle if you plan to visit one of these locationsSeaTac
Tacoma
Lacey
Leavenworth
Olympia
Ocean Shores
Edmonds
Snoqualmie
Tumwater
Tukwila
Renton
Kent
Lynnwood
Ellensburg
Fife
Marysville
Lakewood
Issaquah
Shoreline
Centralia
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Ontario and Seattle flights
Browse other Ontario and Seattle flight options. Last updated on June 28, 2026.
Other flights from Ontario
Browse through other flights departing from Ontario. Flights are based on user searches made on Cheapflights and were last updated on June 28, 2026.
Popular flight searches
Check out other popular destinations found by fellow travelers in 2026
Other flights to Seattle
Explore flights to Seattle departing from other origins. Flights are based on user searches made on Cheapflights and were last updated on June 28, 2026.
Top 5 airlines flying from Ontario to Seattle
Discover the top 5 airlines that operate flights from Ontario to Seattle. 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 June 28, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$86 | Average$215 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$88 | Average$210 | FlexibilityNo cancel fee | On-time85% | |
| Cheapest$103 | Average$278 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$139 | Average$294 | FlexibilityNo cancel fee | On-time75% | |
| Cheapest$150 | Average$268 | FlexibilityNo cancel fee | On-time63% |