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Ontario

$64+ Cheap flights from Seattle to Ontario (SEA - ONT)

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 1/11. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — ONT
Jan 22 — Jan 291
Thu 1/22
Thu 1/29
1 adult, Economy
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Find cheap flights from Seattle to Ontario 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 Seattle/Tacoma Intl to Ontario are usually found in October or March, booked 51 days in advance, depart on a Wednesday or Thursday and return on a Saturday

Cheap flight deals from Seattle to Ontario

Cheapest flights from Seattle to Ontario
Explore the most affordable flight options available from Seattle to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on December 23, 2025.

This Priceline deal was found by Cheapflights users on 12/22. 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.
Wed 12/311:25 pmSEA - ONT
1 stop10h 34mFrontier
Sun 1/115:15 pmONT - SEA
Nonstop2h 53mFrontier
Deal found 12/22$201
This Frontier deal was found by Cheapflights users on 12/20. 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.
Mon 12/2211:06 amSEA - ONT
Nonstop2h 36mFrontier
Thu 1/85:15 pmONT - SEA
Nonstop2h 53mFrontier
Deal found 12/20$223
This CheapOair deal was found by Cheapflights users on 12/21. 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.
Mon 12/296:33 pmSEA - ONT
1 stop26h 44mFrontier
Wed 1/710:45 amONT - SEA
1 stop22h 19mFrontier
Deal found 12/21$233
This CheapOair deal was found by Cheapflights users on 12/20. 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 12/311:25 pmSEA - ONT
1 stop10h 34mFrontier
Wed 1/146:49 pmONT - SEA
1 stop25h 02mFrontier
Deal found 12/20$243
This Travelocity deal was found by Cheapflights users on 12/20. 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 Travelocity is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 12/2311:06 amSEA - ONT
Nonstop2h 36mMultiple Airlines
Mon 1/266:00 amONT - SEA
Nonstop2h 54mMultiple Airlines
Deal found 12/20$244
This Expedia deal was found by Cheapflights users on 12/22. 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 12/319:35 pmSEA - ONT
Nonstop2h 39mMultiple Airlines
Sun 1/115:15 pmONT - SEA
Nonstop2h 53mMultiple Airlines
Deal found 12/22$249
This CheapOair deal was found by Cheapflights users on 12/22. 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.
Mon 12/296:33 pmSEA - ONT
1 stop26h 44mFrontier
Mon 1/56:00 pmONT - SEA
1 stop23h 51mFrontier
Deal found 12/22$254
This Delta deal was found by Cheapflights users on 12/20. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 12/314:57 pmSEA - ONT
1 stop5h 36mDelta
Tue 1/133:30 pmONT - SEA
Nonstop3h 05mDelta
Deal found 12/20$277
This Alaska Airlines deal was found by Cheapflights users on 12/20. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 12/319:35 pmSEA - ONT
Nonstop2h 39mAlaska Airlines
Wed 1/1411:53 amONT - SEA
Nonstop2h 51mAlaska Airlines
Deal found 12/20$278

Find flight deals from Seattle to Ontario

Discover tips and strategies to find the most affordable flight options for your journey from Seattle (SEA) to Ontario (ONT). 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 December 23, 2025.

Most accurate provider

CheapOair
3 stars

Most trusted provider

CheapOair
3 stars

Round-trip from

$122
(CheapOair)

One-way from

$64
(Super.com)

Popular in

December

Cheapest in

October

Average price

$318

Good round-trip deal

$207 or less

Good one-way deal

$120 or less
Provider with most accurate pricing for Seattle/Tacoma Intl-Ontario flight deals.
Search Deals
Provider most trusted by Cheapflights users for Seattle/Tacoma Intl-Ontario flights.
Search Deals
From Seattle/Tacoma Intl to Ontario
Search Deals
One-way flight from Seattle/Tacoma Intl to Ontario
Search Deals
Highest demand for flights based on searches. 12% potential increase in price ($34 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 3% potential price decrease ($8 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 Seattle/Tacoma Intl to Ontario.
Search Deals
Price to beat on a one-way flight from Seattle/Tacoma Intl to Ontario.
Search Deals

Cheapflights Fare Finder

 
Customize your flight search to find flights from Seattle to Ontario 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 December 23, 2025.
Use the filters below to find and compare flights from Seattle to Ontario that are best for you.

Fly from

Seattle

Fly to

Ontario

Route

Depart

Return

Price

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Fri 2/6

9:20 pm-11:56 pm

Nonstop2h 36m

Ontario

Sun 2/8

6:00 am-8:54 am

Nonstop2h 54m

$129

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 2/7

12:31 pm-3:08 pm

Nonstop2h 37m

Ontario

Sun 2/8

6:00 am-8:54 am

Nonstop2h 54m

$129

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 2/26

8:56 pm-11:32 pm

Nonstop2h 36m

Ontario

Mon 3/2

6:14 am-9:09 am

Nonstop2h 55m

$129

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Wed 1/21

6:00 pm-8:36 pm

Nonstop2h 36m

Ontario

Fri 1/23

4:03 pm-6:54 pm

Nonstop2h 51m

$139

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 1/22

8:07 pm-10:51 pm

Nonstop2h 44m

Ontario

Sun 1/25

7:30 am-10:36 am

Nonstop3h 06m

$149

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Fri 2/6

9:50 am-2:05 pm

1 stop4h 15m

Ontario

Sun 2/8

6:05 am-12:20 pm

1 stop6h 15m

$151

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Wed 1/14

2:05 pm-9:45 pm

1 stop7h 40m

Ontario

Sat 1/17

1:00 pm-9:05 pm

1 stop8h 05m

$151

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Wed 1/14

5:15 am-12:25 pm

1 stop7h 10m

Ontario

Sun 1/18

8:55 am-5:50 pm

1 stop8h 55m

$151

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 1/22

9:20 pm-11:56 pm

Nonstop2h 36m

Ontario

Wed 2/4

1:46 pm-10:33 pm

1 stop8h 47m

$152

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 2/19

8:56 pm-11:32 pm

Nonstop2h 36m

$70

Flights are sorted by cheapest round-trip flights first.

Deals found on 12/22

Showing 1-10 of 21 results
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Compare providers for flights from Seattle to Ontario

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 Seattle to Ontario 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
CheapOairPrice Accuracy3 starsTrust Score*3 stars
CheapfaremartPrice Accuracy-Trust Score*1 star
PricelinePrice Accuracy1 starTrust Score*3 stars
JustAirTicketPrice Accuracy-Trust Score*1 star
Justfly.comPrice Accuracy3 starsTrust Score*3 stars
JetabroadPrice Accuracy3 starsTrust Score*1 star

*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 Seattle-Ontario flights, users find the pricing of CheapOair to be most consistent on Cheapflights vs. CheapOair Users can find the same prices on Seattle-Ontario flight deals on Cheapflights vs. CheapOair >95% of the time. Price accuracy is based on data collected from Seattle-Ontario flight searches over the past month and is updated monthly.
  • Most trusted provider: When it comes to deals on Seattle-Ontario 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 Seattle-Ontario 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 Seattle to Ontario

Have a flexible travel schedule? Discover the best time to fly to Ontario from Seattle 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 Seattle to Ontario

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

Use this chart to determine the optimal time to book a round-trip flight from Seattle to Ontario. Price data was last updated on December 19, 2025.

The best time to book flights from Seattle to Ontario is 51 days before your desired departure date. The cost of your flight will likely increase significantly if you book two weeks in advance of your flight.

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

Currently, January is the cheapest month in which you can book a flight from Seattle to Ontario (average of $38). Flying from Seattle to Ontario in July is currently the most expensive (average of $119). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from SEA to ONT?

Find hourly flight availability from Seattle to Ontario. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated December 23, 2025.

A simple way to save on the total cost of your ticket is to fly from Seattle to Ontario at noon. If you’re flexible enough to do this you can expect to save up to 20% on your trip compared to booking a flight in the evening.

What is the cheapest day to fly from Seattle to Ontario?

Use this chart to determine the cheapest time to fly round-trip from Seattle to Ontario. Price data was last updated on December 20, 2025.

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

The best insider tips for Seattle to Ontario 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 Seattle to Ontario trip
Airlines
Frontier

Frontier's UpFront Plus seats offer a guaranteed empty middle seat for added comfort.


Frontier's Zone 1 boarding is available with carry-on purchase or special fare bundles.

Read more about FrontierBy Marisa Garcia
Alaska Airlines

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


Alaska Airlines' Wi-Fi is a flat fee, ideal for business travelers needing connectivity during flights.

Read more about Alaska AirlinesBy Robert Schrader
Airports
SEA

Use SEA Spot Saver for free security screening appointments. Sign up online a few days before your flight to reduce wait times.

Read more about SEABy Brandon Schultz
ONT

Consider renting a car at ONT for easy access to Southern California destinations like Palm Springs and Big Bear.

Read more about ONTBy Bill Fink
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 Ontario

Get insights into the airlines that provide service to Ontario. 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 Ontario. Reviews last updated December 23, 2025.
See what other customers who have flown with Alaska Airlines, Southwest, and Delta from Seattle to Ontario 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
11,506 reviews

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Overall

8.0

Comfort

7.8

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
Alaska Airlines
8.0
Very good
11,506 reviews
Alaska Airlines
8.0
Very good
11,506 reviews

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Overall

8.0

Comfort

7.8

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
Southwest
8.0
Very good
4,253 reviews
Alaska Airlines
8.0
Very good
11,506 reviews

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Overall

8.0

Comfort

7.8

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
Delta
7.9
Good
8,014 reviews
Alaska Airlines
8.0
Very good
11,506 reviews

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Overall

8.0

Comfort

7.8

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
Hawaiian Airlines
7.8
Good
2,820 reviews
Alaska Airlines
8.0
Very good
11,506 reviews

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Overall

8.0

Comfort

7.8

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.
Frontier
5.8
Fair
3,076 reviews
Alaska Airlines
8.0
Very good
11,506 reviews

Crew

8.5

Entertainment

7.0

Food

7.1

Boarding

8.1

Overall

8.0

Comfort

7.8

Reviews

1 / 20
8.0
Excellent

Anonymous,Sep 2025

SEA - MKE

The crew were excellent, flight good, but the actual space for a person to occupy for 4 hours seems to get smaller and smaller 🤣. I am not overweight, and average height….very uncomfortable,, especially when I couldn’t recliner the seat at all, and the pocket in front doesn’t accommodate a water bottle.

Related info for your journey

Find useful and relevant information for your journey from Seattle to Ontario. 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 Seattle to Ontario?

    Booking a flight from Seattle/Tacoma Intl (SEA) to Ontario (ONT) is your only option if you wish to fly from Seattle to Ontario. On a typical day, there are 16 flights from Seattle/Tacoma Intl to Ontario, all of which are around 2h 31m for a nonstop flight. You can also purchase a plane ticket from 5 airlines when you book a flight from Seattle/Tacoma Intl to Ontario.

  • How popular is this Seattle to Ontario flight route?

    This flight path from Seattle/Tacoma Intl to Ontario was viewed by 51 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 Seattle to Ontario?

    A quick flight from Seattle to Ontario can take about 2h 36m. Alaska Airlines provides one of the quickest options available for as low as $129. The distance from Seattle to Ontario is about 956 mi. Generally, flights for this route are nonstop.

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

    Our cheapest airline available from Seattle to Ontario is Frontier. Our recent data shows that you can find tickets from as low as $59 on this airline. Additional options worth looking into are Hawaiian Airlines and Delta, starting at $88 and $109 round-trip. Frontier is priced at 74% lower than the current average price of a flight leaving 3 months from now.

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

    For one-way options, check prices for Frontier. According to our data, you can fly for as low as $46. Users have also found prices from $62 and $78 on Southwest and Hawaiian Airlines, respectively.

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

    Before booking your flight to Ontario from Seattle, check out the most reliable airlines to get you to your destination on time: Virgin Atlantic (97%), KLM (94%), Korean Air( 94%).

  • What are the cheapest flights from Seattle to Ontario?

    Looking at all options, your cheapest flight can be booked for $69. While the most popular route (Seattle/Tacoma Intl - Ontario) can be booked for $99 on average, our data indicates $333 when flying from Seattle to Ontario.

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

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

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

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

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

    Yes. Cheapflights offers flight deals from Seattle to Ontario 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 Seattle to Ontario?

    Currently, January is the cheapest month in which you can book a flight from Seattle to Ontario (average of $38). Flying from Seattle to Ontario in July is currently the most expensive (average of $119). 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

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Top 5 airlines flying from Seattle to Ontario

Discover the top 5 airlines that operate flights from Seattle to Ontario. 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 December 23, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$68Average$175FlexibilityNo cancel feeOn-time62%
Hawaiian AirlinesCheapest$98Average$237FlexibilityNo cancel feeOn-time85%
DeltaCheapest$118Average$257FlexibilityNo cancel feeOn-timeN/A
SouthwestCheapest$130Average$238FlexibilityNo cancel feeOn-time63%
Alaska AirlinesCheapest$156Average$287FlexibilityNo cancel feeOn-time75%

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