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$90+ 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 7/21. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — SEA
Mar 13 — Mar 201
Fri 3/13
Fri 3/20
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

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Cheapflights Tip: The best prices from Ontario to Seattle/Tacoma Intl are usually found in March or January, booked 55 days in advance, depart on a Saturday or Friday and return on a Wednesday

Cheap flight deals from Ontario to Seattle

Cheapest flights from Ontario to Seattle
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 February 11, 2026.

This Kiwi.com deal was found by Cheapflights users on 2/10. 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 3/26:43 pm
ONT
-
SEA
1 stop23h 35m
Frontier
Sun 3/159:35 pm
SEA
-
ONT
1 stop10h 31m
Frontier
Deal found 2/10$131
This CheapOair deal was found by Cheapflights users on 2/9. 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.
Sat 2/286:00 am
ONT
-
SEA
1 stop28h 55m
Frontier
Tue 3/37:33 pm
SEA
-
ONT
1 stop17h 38m
Frontier
Deal found 2/9$144
This Kiwi.com deal was found by Cheapflights users on 2/8. 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 3/122:06 pm
ONT
-
SEA
1 stop6h 14m
Frontier
Sun 3/159:35 pm
SEA
-
ONT
1 stop10h 31m
Frontier
Deal found 2/8$145
This Kiwi.com deal was found by Cheapflights users on 2/9. 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 3/74:02 pm
ONT
-
SEA
Nonstop2h 50m
Hawaiian Airlines
Tue 3/108:30 am
SEA
-
ONT
Nonstop2h 38m
Hawaiian Airlines
Deal found 2/9$148
This Kiwi.com deal was found by Cheapflights users on 2/10. 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 3/23:28 pm
ONT
-
SEA
1 stop26h 50m
Frontier
Sun 3/229:35 pm
SEA
-
ONT
1 stop10h 31m
Frontier
Deal found 2/10$151
This Super.com deal was found by Cheapflights users on 2/8. 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.
Thu 2/266:05 am
ONT
-
SEA
1 stop28h 50m
Frontier
Sat 2/281:16 pm
SEA
-
ONT
1 stop10h 43m
Frontier
Deal found 2/8$152
This CheapOair deal was found by Cheapflights users on 2/9. 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 2/262:08 pm
ONT
-
SEA
1 stop20h 47m
Frontier
Mon 3/29:14 pm
SEA
-
ONT
1 stop15h 57m
Frontier
Deal found 2/9$154
This CheapOair deal was found by Cheapflights users on 2/10. 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 2/257:17 pm
ONT
-
SEA
1 stop24h 51m
Frontier
Tue 3/37:33 pm
SEA
-
ONT
1 stop22h 49m
Frontier
Deal found 2/10$155
This Alaska Airlines deal was found by Cheapflights users on 2/9. 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 3/712:02 pm
ONT
-
SEA
Nonstop2h 50m
Alaska Airlines
Sat 3/148:30 am
SEA
-
ONT
Nonstop2h 38m
Alaska Airlines
Deal found 2/9$157
This Kiwi.com deal was found by Cheapflights users on 2/8. 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 4/611:10 am
ONT
-
SEA
1 stop6h 24m
Frontier
Mon 5/49:35 pm
SEA
-
ONT
1 stop16h 05m
Frontier
Deal found 2/8$158
This Trip.com deal was found by Cheapflights users on 2/8. 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.
Sat 3/76:14 am
ONT
-
SEA
Nonstop2h 55m
Hawaiian Airlines
Mon 3/98:56 pm
SEA
-
ONT
Nonstop2h 36m
Hawaiian Airlines
Deal found 2/8$159
This Frontier deal was found by Cheapflights users on 2/10. 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 4/1612:59 am
ONT
-
SEA
1 stop8h 28m
Frontier
Fri 4/174:20 pm
SEA
-
ONT
1 stop7h 35m
Frontier
Deal found 2/10$160

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 February 11, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$131
(Kiwi.com)

One-way from

$90
(Frontier)

Popular in

July

Cheapest in

March

Average price

$237

Good round-trip deal

$236 or less

Good one-way deal

$145 or less
Provider with most accurate pricing for Ontario-Seattle/Tacoma Intl flight deals.
Search Deals
Provider most trusted by Cheapflights users for Ontario-Seattle/Tacoma Intl flights.
Search Deals
From Ontario to Seattle/Tacoma Intl
Search Deals
One-way flight from Ontario to Seattle/Tacoma Intl
Search Deals
Highest demand for flights based on searches. 5% potential increase in price ($12 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 1% potential price decrease ($3 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in February 2026
Search Deals
Price to beat on a round-trip flight from Ontario to Seattle/Tacoma Intl.
Search Deals
Price to beat on a one-way flight from Ontario to Seattle/Tacoma Intl.
Search Deals

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 February 11, 2026.
Use the filters below to find and compare flights from Ontario to Seattle that are best for you.

Fly from

Ontario

Fly to

Seattle

Route

Depart

Return

Price

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Tue 5/12

3:26 pm-6:17 pm

Nonstop2h 51m

Seattle/Tacoma Intl

Tue 5/19

9:22 pm-11:58 pm

Nonstop2h 36m

$157

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Tue 4/14

2:20 pm-5:24 pm

Nonstop3h 04m

Seattle/Tacoma Intl

Sat 4/18

10:54 am-1:39 pm

Nonstop2h 45m

$157

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 3/7

6:14 am-9:09 am

Nonstop2h 55m

Seattle/Tacoma Intl

Tue 3/10

8:05 pm-10:44 pm

Nonstop2h 39m

$157

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 3/14

6:00 am-8:54 am

Nonstop2h 54m

Seattle/Tacoma Intl

Wed 3/18

2:30 pm-5:13 pm

Nonstop2h 43m

$157

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 3/14

12:02 pm-2:52 pm

Nonstop2h 50m

Seattle/Tacoma Intl

Wed 3/18

9:24 pm-11:59 pm

Nonstop2h 35m

$157

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Tue 4/14

7:00 am-10:07 am

Nonstop3h 07m

Seattle/Tacoma Intl

Wed 4/22

8:25 am-11:13 am

Nonstop2h 48m

$157

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Tue 3/3

4:02 pm-6:52 pm

Nonstop2h 50m

Seattle/Tacoma Intl

Sat 3/7

8:30 am-11:08 am

Nonstop2h 38m

$157

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Thu 4/2

6:00 am-8:55 am

Nonstop2h 55m

Seattle/Tacoma Intl

Wed 4/8

8:30 am-11:18 am

Nonstop2h 48m

$167

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Fri 4/17

5:55 pm-8:55 pm

Nonstop3h 00m

Seattle/Tacoma Intl

Tue 4/21

8:25 am-11:13 am

Nonstop2h 48m

$167

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Fri 4/17

5:55 pm-8:55 pm

Nonstop3h 00m

Seattle/Tacoma Intl

Sat 4/18

10:54 am-1:39 pm

Nonstop2h 45m

$167

Flights are sorted by cheapest round-trip flights first.

Deals found on 2/8

Showing 1-10 of 23 results
1
2
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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 February.
ProviderPrice AccuracyTrust Score*
ExpediaPrice Accuracy1 starTrust Score*3 stars
FlightHubPrice Accuracy3 starsTrust Score*3 stars
Kiwi.comPrice Accuracy3 starsTrust Score*3 stars
CheapflightsfaresPrice Accuracy2 starsTrust Score*2 stars
eDreamsPrice Accuracy3 starsTrust Score*3 stars
CheapOairPrice Accuracy3 starsTrust Score*3 stars
CheapTicketsDealPrice Accuracy3 starsTrust Score*3 stars
CheapfaremartPrice Accuracy-Trust Score*1 star
Justfly.comPrice Accuracy3 starsTrust Score*3 stars
MytripPrice Accuracy2 starsTrust Score*3 stars

*The Trust Score is based on feedback from users after their booking experience. It measures overall satisfaction, helping us identify issues like hidden fees, problems during the ticketing process, and the quality of customer service. This score is our best indicator of the provider's quality and reliability.

  • 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.
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

How far ahead should I book a flight from Ontario to Seattle?

Use this chart to determine the optimal time to book a round-trip flight from Ontario to Seattle. Price data was last updated on February 6, 2026.

To ensure you get the cheapest price possible for a flight from Ontario to Seattle, you should look to book at least 55 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, March is the cheapest month in which you can book a flight from Ontario to Seattle (average of $55). Flying from Ontario to Seattle in July is currently the most expensive (average of $134). 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 February 11, 2026.

It’s typically best to fly out from Ontario to Seattle in the morning. Doing so could potentially save you 10% on the flight price compared to flying in the evening, 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 February 7, 2026.

Travelers seeking maximum savings on their Ontario to Seattle flight should consider departing on Saturday evenings when fares are most often at their lowest. Sunday evenings flights should be avoided if possible as fares are typically the most expensive at this time.

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
Marisa Garcia

Marisa Garcia

Expert on Frontier

Marisa knows planes inside and out, spending 16 years working on aircraft in hangars at airports around the world. She is an aviation industry expert, specialized in airline interiors and regulations. Ten years ago, she pivoted to journalism. She shares her insights in leading aviation, travel, and business publications and on her site FlightChic.

Read more
Robert Schrader

Robert Schrader

Expert on Alaska Airlines

One of the web's original travel bloggers, Robert launched his first site Leave Your Daily Hell in 2009. Since then, he's expanded into destination niche sites (one each for Japan, Thailand and Taiwan), in addition to having written for the inflight magazines of Singapore Airlines and Korean Air. Overall, he's visited nearly 100 countries, and flies business as often as possible.

Read more
Bill Fink

Bill Fink

Expert on ONT

Bill is an award-winning travel writer with extensive credits covering airlines and the aviation industry for publications including AARP, AFAR, The Points Guy and Yahoo. Based in Portland, Oregon, Bill has traveled to more than 75 countries - and been late for his flight in most of them. He once achieved top-level frequent flier status for all of American, Delta and United Airlines during a single year.

Read more
Brandon Schultz

Brandon Schultz

Expert on SEA

Brandon Schultz is an award-winning food and travel writer based in New York City. His work has appeared in Forbes, AAA, Thrillist, Travel + Leisure, and The Daily Meal, among many others, and he is the author of 6 books, including 3 cookbooks.

Read more

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 February 11, 2026.
See what other customers who have flown with Alaska Airlines, Southwest, and Delta 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.
Alaska Airlines
8.0
Very good
11,875 reviews

Overall

8.0

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.1

Reviews

1 / 20
10.0
Excellent

Anonymous,Dec 2025

SJC - SEA

The flight was great. Don’t have to make it better. Everything was OK.
Alaska Airlines
8.0
Very good
11,875 reviews
Alaska Airlines
8.0
Very good
11,875 reviews

Overall

8.0

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.1

Reviews

1 / 20
10.0
Excellent

Anonymous,Dec 2025

SJC - SEA

The flight was great. Don’t have to make it better. Everything was OK.
Southwest
8.0
Very good
4,280 reviews
Alaska Airlines
8.0
Very good
11,875 reviews

Overall

8.0

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.1

Reviews

1 / 20
10.0
Excellent

Anonymous,Dec 2025

SJC - SEA

The flight was great. Don’t have to make it better. Everything was OK.
Delta
7.9
Good
8,180 reviews
Alaska Airlines
8.0
Very good
11,875 reviews

Overall

8.0

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.1

Reviews

1 / 20
10.0
Excellent

Anonymous,Dec 2025

SJC - SEA

The flight was great. Don’t have to make it better. Everything was OK.
Hawaiian Airlines
7.8
Good
2,832 reviews
Alaska Airlines
8.0
Very good
11,875 reviews

Overall

8.0

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.1

Reviews

1 / 20
10.0
Excellent

Anonymous,Dec 2025

SJC - SEA

The flight was great. Don’t have to make it better. Everything was OK.
Frontier
5.7
Fair
3,052 reviews
Alaska Airlines
8.0
Very good
11,875 reviews

Overall

8.0

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.1

Reviews

1 / 20
10.0
Excellent

Anonymous,Dec 2025

SJC - SEA

The flight was great. Don’t have to make it better. Everything was OK.

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.

  • What airports do I use to fly from Ontario to Seattle?

    If you wish to fly to Seattle from Ontario, then you need to book flights from Ontario to Seattle/Tacoma Intl. There are 3 flights from Ontario (ONT) to Seattle/Tacoma Intl (SEA) per day to choose from. Flights to Seattle from Ontario are available from 5 different airlines, which means you should have some options if you want to compare airfare deals. 2h 42m is how long a nonstop flight from Ontario to Seattle/Tacoma Intl typically takes.

  • How popular is this Ontario to Seattle flight route?

    The Ontario to Seattle/Tacoma Intl flight path was viewed by 202 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

  • How long is the flight from Ontario to Seattle?

    There are many flights that can get you from Ontario to Seattle in 2h 51m. Fly via Alaska Airlines to get the fastest option. There are 956 mi between Ontario and Seattle. Most flights are nonstop.

  • What are the cheapest airlines flying from Ontario to Seattle round-trip?

    Cheapflights users have booked flights from Ontario to Seattle round-trip from $80. Other airlines that can offer you cheap pricing are Hawaiian Airlines, from $88, and Delta, from $99. You may be able to fly from Ontario to Seattle for 63% less than the average price by searching for these airlines.

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

    The cheapest airlines for a one-way flight from Ontario to Seattle are Frontier ($44), Southwest ($78), and United Airlines ($88).

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

    Consider Aeromexico (100%), Japan Airlines (98%) or KLM (93%) when booking your flight. These represent the most reliable airlines when flying from Ontario to Seattle.

  • What are the cheapest flights from Ontario to Seattle?

    While on average a flight from Ontario to Seattle is generally $466, our data shows the cheapest flight currently is $98. When looking at the most popular route, (Ontario - Seattle/Tacoma Intl), you can expect to pay $148 for that flight.

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

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

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

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

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

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

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

    Currently, March is the cheapest month in which you can book a flight from Ontario to Seattle (average of $55). Flying from Ontario to Seattle in July is currently the most expensive (average of $134). 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.

See more FAQs

Traveling to a place near Seattle?

Book flights to Seattle if you plan to visit one of these locations
Tacoma
SeaTac
Lakewood
Ocean Shores
Olympia
Lynnwood
Edmonds
Lacey
Kent
Renton
Puyallup
Kirkland
Tukwila
Fife
Aberdeen
Shoreline
Marysville
Centralia
Federal Way
Chehalis

Browse thousands of different options on Cheapflights for your next trip

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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 February 11, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$80Average$179FlexibilityNo cancel feeOn-time62%
Hawaiian AirlinesCheapest$88Average$221FlexibilityNo cancel feeOn-time85%
DeltaCheapest$99Average$250FlexibilityNo cancel feeOn-timeN/A
Alaska AirlinesCheapest$140Average$269FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$150Average$243FlexibilityNo cancel feeOn-time63%

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