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$67+ 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 1/25. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — SEA
ene. 27 — feb. 31
mar. 1/27
mar. 2/3
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 February, 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 diciembre 28, 2025.

This CheapOair deal was found by Cheapflights users on 12/26. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
lun. 12/292:45 pmONT - SEA
Nonstop2h 53mFrontier
sáb. 1/102:49 pmSEA - ONT
1 stop8h 25mFrontier
Deal found 12/26$256
This Kiwi.com deal was found by Cheapflights users on 12/27. 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.
sáb. 12/273:50 pmONT - SEA
Nonstop2h 53mFrontier
sáb. 1/3112:54 pmSEA - ONT
1 stop5h 46mFrontier
Deal found 12/27$260
This CheapOair deal was found by Cheapflights users on 12/26. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
vie. 12/262:45 pmONT - SEA
Nonstop2h 53mFrontier
dom. 1/116:48 pmSEA - ONT
Nonstop2h 35mFrontier
Deal found 12/26$263
This Kiwi.com deal was found by Cheapflights users on 12/27. 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.
sáb. 12/273:50 pmONT - SEA
Nonstop2h 53mMultiple Airlines
sáb. 1/316:00 pmSEA - ONT
Nonstop2h 36mMultiple Airlines
Deal found 12/27$269
This Frontier deal was found by Cheapflights users on 12/26. 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.
lun. 12/292:45 pmONT - SEA
Nonstop2h 53mFrontier
jue. 1/89:23 pmSEA - ONT
1 stop10h 13mFrontier
Deal found 12/26$276
This Frontier deal was found by Cheapflights users on 12/26. 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.
mar. 12/302:45 pmONT - SEA
Nonstop2h 53mFrontier
lun. 1/52:54 pmSEA - ONT
1 stop9h 05mFrontier
Deal found 12/26$301
This Kiwi.com deal was found by Cheapflights users on 12/27. 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.
lun. 12/292:45 pmONT - SEA
Nonstop2h 53mFrontier
sáb. 1/312:16 pmSEA - ONT
Nonstop2h 39mFrontier
Deal found 12/27$303
This Cheapflightsfares deal was found by Cheapflights users on 12/26. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
lun. 12/292:45 pmONT - SEA
Nonstop2h 53mFrontier
vie. 1/211:06 amSEA - ONT
Nonstop2h 36mFrontier
Deal found 12/26$306
This CheapOair deal was found by Cheapflights users on 12/26. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
vie. 12/262:45 pmONT - SEA
Nonstop2h 53mFrontier
sáb. 1/312:16 pmSEA - ONT
Nonstop2h 39mFrontier
Deal found 12/26$308
This Frontier deal was found by Cheapflights users on 12/26. 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.
sáb. 12/273:50 pmONT - SEA
Nonstop2h 53mFrontier
vie. 1/22:54 pmSEA - ONT
1 stop9h 05mFrontier
Deal found 12/26$310

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 diciembre 28, 2025.

Most accurate provider

CheapOair
3 stars

Most trusted provider

CheapOair
3 stars

Round-trip from

$119
(Alaska Airlines)

One-way from

$67
(Kiwi.com)

Popular in

December

Cheapest in

January

Average price

$256

Good round-trip deal

$187 or less

Good one-way deal

$152 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
High demand for flights, 0% potential price rise
Search Deals
Cheapest flight prices on average. 1% potential price decrease ($4 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in December 2025
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 diciembre 28, 2025.
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

sáb. 1/24

4:03 pm-6:54 pm

Nonstop2h 51m

Seattle/Tacoma Intl

sáb. 1/31

6:00 pm-8:36 pm

Nonstop2h 36m

$119

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

jue. 1/29

3:30 pm-6:35 pm

Nonstop3h 05m

Seattle/Tacoma Intl

mar. 2/3

8:00 pm-10:44 pm

Nonstop2h 44m

$119

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

lun. 1/26

6:00 am-8:54 am

Nonstop2h 54m

Seattle/Tacoma Intl

lun. 2/2

9:20 pm-11:56 pm

Nonstop2h 36m

$119

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

jue. 1/29

3:30 pm-6:35 pm

Nonstop3h 05m

Seattle/Tacoma Intl

jue. 2/5

11:15 am-1:56 pm

Nonstop2h 41m

$119

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

sáb. 1/31

4:03 pm-6:54 pm

Nonstop2h 51m

Seattle/Tacoma Intl

mar. 2/3

6:00 pm-8:36 pm

Nonstop2h 36m

$119

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

vie. 2/13

3:30 pm-6:33 pm

Nonstop3h 03m

Seattle/Tacoma Intl

mar. 2/17

4:40 pm-11:49 pm

1 stop7h 09m

$129

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

mar. 2/17

7:30 am-10:34 am

Nonstop3h 04m

Seattle/Tacoma Intl

mar. 2/24

7:00 pm-11:49 pm

1 stop4h 49m

$129

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

sáb. 3/21

6:00 am-12:25 pm

1 stop6h 25m

Seattle/Tacoma Intl

sáb. 3/28

5:30 pm-10:48 pm

1 stop5h 18m

$139

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

jue. 1/29

6:00 am-12:33 pm

1 stop6h 33m

Seattle/Tacoma Intl

dom. 2/1

5:00 am-12:16 pm

1 stop7h 16m

$139

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

vie. 1/23

3:20 pm-11:05 pm

1 stop7h 45m

Seattle/Tacoma Intl

sáb. 1/24

11:40 am-6:35 pm

2 stops6h 55m

$156

Flights are sorted by cheapest round-trip flights first.

Deals found on 12/27

Showing 1-10 of 23 results
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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 December.
ProviderPrice AccuracyTrust Score*
ExpediaPrice Accuracy2 starsTrust Score*3 stars
FlightHubPrice Accuracy3 starsTrust Score*1 star
eDreamsPrice Accuracy3 starsTrust Score*3 stars
CheapflightsfaresPrice Accuracy3 starsTrust Score*2 stars
Kiwi.comPrice Accuracy3 starsTrust Score*3 stars
CheapOairPrice Accuracy3 starsTrust Score*3 stars
CheapfaremartPrice Accuracy-Trust Score*1 star
CheapTicketsDealPrice Accuracy3 starsTrust Score*3 stars
Justfly.comPrice Accuracy3 starsTrust Score*3 stars
MytripPrice Accuracy3 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 CheapOair to be most consistent on Cheapflights vs. CheapOair Users can find the same prices on Ontario-Seattle flight deals on Cheapflights vs. CheapOair >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 CheapOair the most. CheapOair 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 December 26, 2025.

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, January is the cheapest month in which you can book a flight from Ontario to Seattle (average of $38). 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 diciembre 28, 2025.

It’s typically best to fly out from Ontario to Seattle in the morning. Doing so could potentially save you 13% 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 December 27, 2025.

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
Airlines
Frontier

Frontier offers extra comfort seats with 32” separation for a fee, ideal for taller passengers.


Frontier's Board First option allows early boarding for carry-on bag purchasers and elite members.

Read more about FrontierBy Marisa Garcia
Alaska Airlines

Alaska Airlines offers Wi-Fi for a flat fee, ideal for business travelers needing connectivity.


Alaska's Premium Class offers extra legroom and free cocktails, enhancing comfort on short flights.

Read more about Alaska AirlinesBy Robert Schrader
Airports
ONT

ONT offers quick security checks compared to LAX, making it ideal for business travelers seeking efficiency.

Read more about ONTBy Bill Fink
SEA

Use the Link light rail for a cost-effective trip to downtown Seattle, taking less than 40 minutes from SEA.

Read more about SEABy Brandon Schultz
Our travel experts
Marisa Garcia

Marisa Garcia

Expert on Frontier

Marisa Garcia

Marisa Garcia

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

Robert Schrader

Robert Schrader

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 Fink

Bill Fink

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

Brandon Schultz

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 diciembre 28, 2025.
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
11,549 reviews

Overall

8.0

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Comfort

7.8

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
11,549 reviews
Alaska Airlines
8.0
Very good
11,549 reviews

Overall

8.0

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Comfort

7.8

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
4,256 reviews
Alaska Airlines
8.0
Very good
11,549 reviews

Overall

8.0

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Comfort

7.8

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
8,021 reviews
Alaska Airlines
8.0
Very good
11,549 reviews

Overall

8.0

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Comfort

7.8

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
2,819 reviews
Alaska Airlines
8.0
Very good
11,549 reviews

Overall

8.0

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Comfort

7.8

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
5.8
Fair
3,070 reviews
Alaska Airlines
8.0
Very good
11,549 reviews

Overall

8.0

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Comfort

7.8

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 14 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 50m 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 or Delta 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 $78. 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 Delta ($86).

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

    Consider Volaris (100%), Virgin Atlantic (95%) or KLM (95%) 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 $464, our data shows the cheapest flight currently is $75. When looking at the most popular route, (Ontario - Seattle/Tacoma Intl), you can expect to pay $119 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, January is the cheapest month in which you can book a flight from Ontario to Seattle (average of $38). 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
Edmonds
Lynnwood
Renton
Puyallup
Kirkland
Kent
Tukwila
Cle Elum
Marysville
Fife
Aberdeen
Shoreline
Centralia
Federal Way
Chehalis

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Alternative routes for Ontario to Seattle

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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 diciembre 28, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$85Average$178FlexibilityNo cancel feeOn-time62%
Hawaiian AirlinesCheapest$98Average$248FlexibilityNo cancel feeOn-time85%
DeltaCheapest$117Average$251FlexibilityNo cancel feeOn-timeN/A
Alaska AirlinesCheapest$146Average$266FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$150Average$241FlexibilityNo cancel feeOn-time63%

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