$65+ 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 10/3. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — SEA
Sep 15 — Sep 221
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 56 days in advance, depart on a Friday or Thursday 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 August 16, 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 August 16, 2026.
This Vliegwinkel deal was found by Cheapflights users on 8/13. 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 Vliegwinkel is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/195:34 pm -
Nonstop2h 56m
Mon 9/2110:53 am -
Nonstop2h 52m
Deal found 8/13![Frontier logo]()
$167
This Frontier deal was found by Cheapflights users on 8/13. 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 9/54:44 pm -
Nonstop2h 49m
Wed 9/910:53 am -
Nonstop2h 52m
Deal found 8/13![Frontier logo]()
$168
This Super.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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/125:34 pm -
Nonstop2h 56m
Sun 9/1310:53 am -
Nonstop2h 52m
Deal found 8/16![Frontier logo]()
$170
This Super.com deal was found by Cheapflights users on 8/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/95:44 pm -
Nonstop2h 56m
Sun 9/1310:53 am -
Nonstop2h 52m
Deal found 8/14![Frontier logo]()
$171
This Frontier deal was found by Cheapflights users on 8/12. 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.
Sun 9/65:17 pm -
Nonstop2h 45m
Sat 9/1210:53 am -
Nonstop2h 52m
Deal found 8/12![Frontier logo]()
$173
This Kiwi.com deal was found by Cheapflights users on 8/13. 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 9/165:44 pm -
Nonstop2h 56m
Tue 9/2210:57 am -
1 stop6h 02m
Deal found 8/13![Frontier logo]()
$174
This Kiwi.com deal was found by Cheapflights users on 8/11. 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 9/185:44 pm -
Nonstop2h 56m
Sun 9/279:45 pm -
1 stop9h 19m
Deal found 8/11![Frontier logo]()
$175
This Super.com deal was found by Cheapflights users on 8/12. 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.
Fri 9/255:44 pm -
Nonstop2h 56m
Mon 9/2810:53 am -
Nonstop2h 52m
Deal found 8/12![Frontier logo]()
$176
This Kiwi.com deal was found by Cheapflights users on 8/13. 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 9/125:34 pm -
Nonstop2h 56m
Mon 9/149:45 pm -
1 stop11h 24m
Deal found 8/13![Frontier logo]()
$177
This Frontier deal was found by Cheapflights users on 8/12. 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 10/75:44 pm -
Nonstop2h 56m
Sat 10/1011:15 am -
Nonstop2h 48m
Deal found 8/12![Frontier logo]()
$178
This Kiwi.com deal was found by Cheapflights users on 8/13. 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 9/1111:45 am -
1 stop27h 23m
Mon 9/2810:53 am -
Nonstop2h 52m
Deal found 8/13![Frontier logo]()
$179
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 August 16, 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 August 16, 2026.
This Delta deal was found by Cheapflights users on 8/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/156:00 am -
Nonstop3h 00m
Tue 9/227:50 pm -
Nonstop2h 50m
Deal found 8/14![Delta logo]()
$247
This Southwest deal was found by Cheapflights users on 8/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/198:35 am -
1 stop5h 05m
Wed 9/238:30 am -
2 stops7h 35m
Deal found 8/15![Southwest logo]()
$272
This Alaska Airlines deal was found by Cheapflights users on 8/11. 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 9/153:14 pm -
Nonstop2h 42m
Sun 9/208:23 am -
Nonstop2h 53m
Deal found 8/11![Alaska Airlines logo]()
$283
This Delta deal was found by Cheapflights users on 8/11. 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 9/106:00 pm -
Nonstop2h 50m
Tue 9/157:50 pm -
Nonstop2h 50m
Deal found 8/11![Delta logo]()
$262
This Southwest deal was found by Cheapflights users on 8/13. 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 10/305:15 pm -
2 stops6h 25m
Mon 11/25:15 am -
1 stop5h 35m
Deal found 8/13![Southwest logo]()
$276
This Delta deal was found by Cheapflights users on 8/12. 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 9/126:00 pm -
Nonstop2h 50m
Sun 9/138:20 am -
Nonstop2h 54m
Deal found 8/12![Delta logo]()
$262
This Delta deal was found by Cheapflights users on 8/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 9/146:00 pm -
Nonstop2h 50m
Mon 9/218:20 am -
Nonstop2h 54m
Deal found 8/15![Delta logo]()
$277
This Delta deal was found by Cheapflights users on 8/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/96:20 am -
Nonstop3h 04m
Sun 10/112:30 pm -
Nonstop2h 42m
Deal found 8/14![Delta logo]()
$278
This Southwest deal was found by Cheapflights users on 8/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/25:15 pm -
2 stops6h 25m
Sun 10/49:35 am -
1 stop4h 05m
Deal found 8/14![Southwest logo]()
$342
This Delta deal was found by Cheapflights users on 8/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/2511:54 am -
Nonstop2h 56m
Mon 9/288:20 am -
Nonstop2h 54m
Deal found 8/15![Delta logo]()
$278
Last-minute flights from Ontario to SeattleDiscover last-minute flight deals from Ontario to Seattle. Data last updated August 16, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Seattle. Data last updated August 16, 2026 and is based on user searches.
This Frontier deal was found by Cheapflights users on 8/11. 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 9/14:44 pm -
Nonstop2h 49m
Thu 9/104:27 pm -
1 stop7h 20m
Deal found 8/11![Frontier logo]()
$178
This Frontier deal was found by Cheapflights users on 8/13. 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 9/54:44 pm -
Nonstop2h 49m
Wed 9/910:53 am -
Nonstop2h 52m
Deal found 8/13![Frontier logo]()
$168
This Frontier deal was found by Cheapflights users on 8/12. 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.
Sun 9/65:17 pm -
Nonstop2h 45m
Sat 9/1210:53 am -
Nonstop2h 52m
Deal found 8/12![Frontier logo]()
$173
This Super.com deal was found by Cheapflights users on 8/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/95:44 pm -
Nonstop2h 56m
Sun 9/1310:53 am -
Nonstop2h 52m
Deal found 8/14![Frontier logo]()
$171
This Kiwi.com deal was found by Cheapflights users on 8/13. 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 9/1111:45 am -
1 stop27h 23m
Mon 9/2810:53 am -
Nonstop2h 52m
Deal found 8/13![Frontier logo]()
$179
This Super.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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/125:34 pm -
Nonstop2h 56m
Sun 9/1310:53 am -
Nonstop2h 52m
Deal found 8/16![Frontier logo]()
$170
This Kiwi.com deal was found by Cheapflights users on 8/13. 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 9/125:34 pm -
Nonstop2h 56m
Mon 9/149:45 pm -
1 stop11h 24m
Deal found 8/13![Frontier logo]()
$177
This Kiwi.com deal was found by Cheapflights users on 8/13. 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 9/165:44 pm -
Nonstop2h 56m
Tue 9/2210:57 am -
1 stop6h 02m
Deal found 8/13![Frontier logo]()
$174
This Kiwi.com deal was found by Cheapflights users on 8/11. 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 9/185:44 pm -
Nonstop2h 56m
Sun 9/279:45 pm -
1 stop9h 19m
Deal found 8/11![Frontier logo]()
$175
This Vliegwinkel deal was found by Cheapflights users on 8/13. 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 Vliegwinkel is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/195:34 pm -
Nonstop2h 56m
Mon 9/2110:53 am -
Nonstop2h 52m
Deal found 8/13![Frontier logo]()
$167
This Super.com deal was found by Cheapflights users on 8/12. 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.
Fri 9/255:44 pm -
Nonstop2h 56m
Mon 9/2810:53 am -
Nonstop2h 52m
Deal found 8/12![Frontier logo]()
$176
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 August 16, 2026.
Search for one-way flight options from Ontario to Seattle. Find affordable one-way fares based on user searches. Data last updated August 16, 2026.
This Frontier deal was found by Cheapflights users on 8/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/35:34 pm -
Nonstop2h 56m
Deal found 8/15![Frontier logo]()
$65
This Kiwi.com deal was found by Cheapflights users on 8/12. 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 9/1111:45 am -
1 stop27h 23m
Deal found 8/12![Frontier logo]()
$70
This Kiwi.com deal was found by Cheapflights users on 8/11. 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 11/85:05 pm -
Nonstop2h 56m
Deal found 8/11![Frontier logo]()
$71
This Super.com deal was found by Cheapflights users on 8/12. 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 11/75:05 pm -
Nonstop2h 56m
Deal found 8/12![Frontier logo]()
$72
This Priceline deal was found by Cheapflights users on 8/13. 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 Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/195:34 pm -
Nonstop2h 56m
Deal found 8/13![Frontier logo]()
$73
This Kiwi.com deal was found by Cheapflights users on 8/13. 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 11/165:05 pm -
Nonstop2h 56m
Deal found 8/13![Frontier logo]()
$74
This Kiwi.com deal was found by Cheapflights users on 8/12. 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 11/145:05 pm -
Nonstop2h 56m
Deal found 8/12![Frontier logo]()
$75
This Kiwi.com deal was found by Cheapflights users on 8/11. 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 11/95:05 pm -
Nonstop2h 56m
Deal found 8/11![Frontier logo]()
$80
This FlightHub deal was found by Cheapflights users on 8/11. 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.
Sun 10/45:44 pm -
Nonstop2h 56m
Deal found 8/11![Frontier logo]()
$82
This Super.com deal was found by Cheapflights users on 8/12. 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 9/54:44 pm -
Nonstop2h 49m
Deal found 8/12![Frontier logo]()
$83
This Kiwi.com deal was found by Cheapflights users on 8/12. 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 11/105:05 pm -
Nonstop2h 56m
Deal found 8/12![Frontier logo]()
$84
This Kiwi.com deal was found by Cheapflights users on 8/13. 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 11/115:05 pm -
Nonstop2h 56m
Deal found 8/13![Frontier logo]()
$85
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 August 16, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $167 (Vliegwinkel) |
One-way from | $65 (Frontier) |
Popular in | July |
Cheapest in | January |
Average price | $279 |
Good round-trip deal | $239 or less |
Good one-way deal | $159 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 August 16, 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 Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Tue 9/15
6:00 am-9:00 am
Nonstop3h 00m
Seattle/Tacoma Intl
Tue 9/22
7:50 pm-10:40 pm
Nonstop2h 50m
$247
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Thu 9/10
6:00 pm-8:50 pm
Nonstop2h 50m
Seattle/Tacoma Intl
Tue 9/15
7:50 pm-10:40 pm
Nonstop2h 50m
$262
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Sat 9/12
6:00 pm-8:50 pm
Nonstop2h 50m
Seattle/Tacoma Intl
Sun 9/13
8:20 am-11:14 am
Nonstop2h 54m
$262
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Sat 9/19
8:35 am-1:40 pm
1 stop5h 05m
Seattle/Tacoma Intl
Wed 9/23
8:30 am-4:05 pm
2 stops7h 35m
$272
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Fri 10/30
5:15 pm-11:40 pm
2 stops6h 25m
Seattle/Tacoma Intl
Mon 11/2
5:15 am-10:50 am
1 stop5h 35m
$276
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Mon 9/14
6:00 pm-8:50 pm
Nonstop2h 50m
Seattle/Tacoma Intl
Mon 9/21
8:20 am-11:14 am
Nonstop2h 54m
$277
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Fri 10/9
6:20 am-9:24 am
Nonstop3h 04m
Seattle/Tacoma Intl
Sun 10/11
2:30 pm-5:12 pm
Nonstop2h 42m
$278
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Fri 9/25
11:54 am-2:50 pm
Nonstop2h 56m
Seattle/Tacoma Intl
Mon 9/28
8:20 am-11:14 am
Nonstop2h 54m
$278
Quickest round-trip
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Tue 9/15
3:14 pm-5:56 pm
Nonstop2h 42m
Seattle/Tacoma Intl
Sun 9/20
8:23 am-11:16 am
Nonstop2h 53m
$283
OntarioSeattle
ONT Ontario - SEA Seattle/Tacoma Intl
ONTSEA
Ontario
Fri 10/2
5:15 pm-11:40 pm
2 stops6h 25m
Seattle/Tacoma Intl
Sun 10/4
9:35 am-1:40 pm
1 stop4h 05m
$342
Showing 1-10 of 20 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 August.
| 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 Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy2 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 43 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 $196). Flying from Ontario to Seattle in July is currently the most expensive (average of $337). 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 August 16, 2026.
It’s typically best to fly out from Ontario to Seattle in the afternoon. Doing so could potentially save you 22% on the flight price compared to flying in the morning, 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 August 8, 2026.
Travelers seeking maximum savings on their Ontario to Seattle flight should consider departing on Saturday afternoons when fares are most often at their lowest. Saturday evenings 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 134 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 at night 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 5% 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 August 16, 2026.
See what other customers who have flown with Southwest,Alaska Airlines, 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.
Comfort
8.0
Food
7.0
Boarding
8.1
Entertainment
7.5
Overall
8.0
Crew
8.6
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Comfort
8.0
Food
7.0
Boarding
8.1
Entertainment
7.5
Overall
8.0
Crew
8.6
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Comfort
8.0
Food
7.0
Boarding
8.1
Entertainment
7.5
Overall
8.0
Crew
8.6
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Comfort
8.0
Food
7.0
Boarding
8.1
Entertainment
7.5
Overall
8.0
Crew
8.6
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Comfort
8.0
Food
7.0
Boarding
8.1
Entertainment
7.5
Overall
8.0
Crew
8.6
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Comfort
8.0
Food
7.0
Boarding
8.1
Entertainment
7.5
Overall
8.0
Crew
8.6
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
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
Renton
Tacoma
Lacey
Leavenworth
Olympia
Tukwila
Edmonds
Snoqualmie
Lynnwood
Tumwater
Centralia
Puyallup
Marysville
Kent
Ellensburg
Fife
Ocean Shores
Lakewood
Poulsbo
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Ontario and Seattle flights
Browse other Ontario and Seattle flight options. Last updated on August 16, 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 August 16, 2026.
Popular flight searches
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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 August 16, 2026.
Top 6 airlines flying from Ontario to Seattle
Discover the top 6 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 August 16, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$85 | Average$225 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$98 | Average$210 | FlexibilityNo cancel fee | On-time85% | |
| Cheapest$100 | Average$287 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$139 | Average$306 | FlexibilityNo cancel fee | On-time75% | |
| Cheapest$150 | Average$296 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$176 | Average$396 | FlexibilityNo cancel fee | On-time69% |