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$92+ 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 9/5. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — ONT
Aug 26 — Sep 21
Tue 8/26
Tue 9/2
1 adult, Economy
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Cheapflights Tip: The best prices from Seattle/Tacoma Intl to Ontario are usually found in September or October, booked 72 days in advance, depart on a Saturday or Tuesday and return on a Friday

Cheap 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 August 21, 2025.

Round-trip from

$114
(CheapOair)

One-way from

$93
(Cheapflightsfares)

Popular in

December

Cheapest in

September

Average price

$177

Good round-trip deal

$150 or less

Good one-way deal

$121 or less
From Seattle/Tacoma Intl to Ontario
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One-way flight from Seattle/Tacoma Intl to Ontario
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Highest demand for flights based on searches. 6% potential increase in price ($13 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease ($6 potential savings vs. average RT price).
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Average for round-trip flights in August 2025
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Price to beat on a round-trip flight from Seattle/Tacoma Intl to Ontario.
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Price to beat on a one-way flight from Seattle/Tacoma Intl to Ontario.
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Find 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 August 21, 2025.

This Frontier deal was found by Cheapflights users on 8/20. 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.
Sun 10/128:28 amSEA - ONT
Nonstop2h 40mFrontier
Mon 10/1310:30 amONT - SEA
Nonstop2h 56mFrontier
Deal found 8/20$114
This Cheapflightsfares deal was found by Cheapflights users on 8/21. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/164:26 pmSEA - ONT
1 stop5h 29mFrontier
Mon 10/2010:30 amONT - SEA
Nonstop2h 56mFrontier
Deal found 8/21$115
This Cheapflightsfares deal was found by Cheapflights users on 8/20. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/212:05 pmSEA - ONT
Nonstop2h 48mFrontier
Mon 10/68:43 amONT - SEA
Nonstop2h 58mFrontier
Deal found 8/20$116
This Frontier deal was found by Cheapflights users on 8/19. 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 9/221:47 pmSEA - ONT
1 stop7h 09mFrontier
Fri 10/38:43 amONT - SEA
Nonstop2h 58mFrontier
Deal found 8/19$117
This Mytrip deal was found by Cheapflights users on 8/21. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/512:30 pmSEA - ONT
Nonstop2h 48mFrontier
Fri 9/124:08 pmONT - SEA
1 stop8h 22mFrontier
Deal found 8/21$118
This Frontier deal was found by Cheapflights users on 8/19. 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 9/207:00 amSEA - ONT
1 stop12h 54mFrontier
Sun 9/218:13 amONT - SEA
Nonstop2h 58mFrontier
Deal found 8/19$119
This Frontier deal was found by Cheapflights users on 8/20. 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.
Thu 9/1812:05 pmSEA - ONT
Nonstop2h 48mFrontier
Mon 10/2010:30 amONT - SEA
Nonstop2h 56mFrontier
Deal found 8/20$120
This CheapOair deal was found by Cheapflights users on 8/21. 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.
Fri 10/108:43 pmSEA - ONT
1 stop27h 07mFrontier
Mon 10/1310:30 amONT - SEA
Nonstop2h 56mFrontier
Deal found 8/21$121
This Cheapflightsfares deal was found by Cheapflights users on 8/19. 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.
Fri 9/512:30 pmSEA - ONT
Nonstop2h 48mFrontier
Sun 9/78:13 amONT - SEA
Nonstop2h 58mFrontier
Deal found 8/19$122
This Mytrip deal was found by Cheapflights users on 8/20. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/108:28 amSEA - ONT
Nonstop2h 40mFrontier
Sun 10/1210:30 amONT - SEA
Nonstop2h 56mFrontier
Deal found 8/20$123
This FlightHub deal was found by Cheapflights users on 8/18. 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.
Thu 10/26:12 amSEA - ONT
1 stop13h 42mFrontier
Sun 10/58:13 amONT - SEA
Nonstop2h 58mFrontier
Deal found 8/18$125

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 August 21, 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 10/10

8:28 am-11:08 am

Nonstop2h 40m

Ontario

Mon 10/13

10:30 am-1:26 pm

Nonstop2h 56m

$114

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sun 10/12

8:28 am-11:08 am

Nonstop2h 40m

Ontario

Mon 10/13

10:30 am-1:26 pm

Nonstop2h 56m

$114

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 10/23

4:26 pm-9:55 pm

1 stop5h 29m

Ontario

Sun 10/26

10:30 am-1:26 pm

Nonstop2h 56m

$114

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Fri 9/19

12:30 pm-3:18 pm

Nonstop2h 48m

Ontario

Mon 10/20

10:30 am-1:26 pm

Nonstop2h 56m

$114

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 10/16

4:26 pm-9:55 pm

1 stop5h 29m

Ontario

Mon 10/20

10:30 am-1:26 pm

Nonstop2h 56m

$115

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Fri 10/17

8:28 am-11:08 am

Nonstop2h 40m

Ontario

Fri 10/24

10:30 am-1:26 pm

Nonstop2h 56m

$116

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Fri 9/26

12:30 pm-3:18 pm

Nonstop2h 48m

Ontario

Mon 9/29

6:00 am-3:41 pm

1 stop9h 41m

$117

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 9/4

12:05 pm-2:53 pm

Nonstop2h 48m

Ontario

Sun 9/7

8:59 pm-12:30 am

1 stop27h 31m

$118

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 9/20

7:00 am-7:54 pm

1 stop12h 54m

Ontario

Sun 9/21

8:13 am-11:11 am

Nonstop2h 58m

$118

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Tue 9/16

7:00 am-7:54 pm

1 stop12h 54m

Ontario

Thu 9/18

8:13 am-11:11 am

Nonstop2h 58m

$118

Flights are sorted by cheapest round-trip flights first.

Deals found on 8/19

Showing 1-10 of 16 results
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The best insider tips for Seattle to Ontario flights

Snippets provided in this section are AI-generated based on a summarization of Cheapflights-commissioned articles. The articles are presented as-is, for general informational purposes only, and may not be up-to-date. The opinions contained in the articles are original to the author and reflect their authentic experience, which may vary significantly from the experience of others.
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

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 August 8, 2025.

The best time to book flights from Seattle to Ontario is 72 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, August is the cheapest month in which you can book a flight from Seattle to Ontario (average of $246). Flying from Seattle to Ontario in March is currently the most expensive (average of $328). 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 August 21, 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 22% on your trip compared to booking a flight in the morning.

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 August 17, 2025.

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

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 August 21, 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
10,000 reviews

Overall

8.0

Boarding

8.1

Crew

8.5

Food

7.1

Entertainment

7.0

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Boarding

8.1

Crew

8.5

Food

7.1

Entertainment

7.0

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Southwest
8.0
Very good
4,245 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Boarding

8.1

Crew

8.5

Food

7.1

Entertainment

7.0

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Delta
8.0
Very good
7,981 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Boarding

8.1

Crew

8.5

Food

7.1

Entertainment

7.0

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Hawaiian Airlines
7.8
Good
2,672 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Boarding

8.1

Crew

8.5

Food

7.1

Entertainment

7.0

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Frontier
5.8
Fair
3,207 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Overall

8.0

Boarding

8.1

Crew

8.5

Food

7.1

Entertainment

7.0

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.

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 15 flights from Seattle/Tacoma Intl to Ontario, all of which are around 2h 32m for a nonstop flight. You can also purchase a plane ticket from 6 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 62 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 40m. Frontier provides one of the quickest options available for as low as $114. 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 $65 on this airline. Additional options worth looking into are Spirit Airlines and Hawaiian Airlines, starting at $72 and $98 round-trip. Frontier is priced at 68% lower than the current average price of a flight leaving 3 months from now.

  • 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: Scandinavian Airlines (91%), SkyWest Airlines (90%), WestJet( 89%).

  • What are the cheapest flights from Seattle to Ontario?

    Looking at all options, your cheapest flight can be booked for $92. While the most popular route (Seattle/Tacoma Intl - Ontario) can be booked for $88 on average our data indicates $191 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, August is the cheapest month in which you can book a flight from Seattle to Ontario (average of $246). Flying from Seattle to Ontario in March is currently the most expensive (average of $328). 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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Alternative routes for Seattle to Ontario

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Top 6 airlines flying from Seattle to Ontario

Discover the top 6 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 August 21, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$65Average$159FlexibilityNo cancel feeOn-time62%
Spirit AirlinesCheapest$72Average$100FlexibilityNo cancel feeOn-time65%
Hawaiian AirlinesCheapest$98Average$241FlexibilityNo cancel feeOn-time85%
DeltaCheapest$117Average$257FlexibilityNo cancel feeOn-timeN/A
Alaska AirlinesCheapest$141Average$273FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$176Average$291FlexibilityNo cancel feeOn-time63%

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