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$89+ 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 9/4. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — ONT
Aug 3 — Aug 101
Sun 8/3
Sun 8/10
1 adult, Economy
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Cheapflights Tip: The best prices from Seattle/Tacoma Intl to Ontario are usually found in September or August, booked 72 days in advance, depart on a Thursday or Saturday 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 July 29, 2025.

Round-trip from

$138
(Frontier)

One-way from

$89
(United Airlines)

Popular in

December

Cheapest in

September

Average price

$248

Good round-trip deal

$159 or less

Good one-way deal

$109 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. 7% potential increase in price ($17 potential increase over avg. RT price).
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Cheapest flight prices on average. 3% potential price decrease ($6 potential savings vs. average RT price).
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Average for round-trip flights in July 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 July 29, 2025.

This Frontier deal was found by Cheapflights users on 7/28. 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.
Fri 9/1912:30 pmSEA - ONT
Nonstop2h 48mFrontier
Thu 9/258:13 amONT - SEA
Nonstop2h 58mFrontier
Deal found 7/28$138
This Alaska Airlines deal was found by Cheapflights users on 7/28. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/1611:25 amSEA - ONT
Nonstop2h 47mAlaska Airlines
Wed 9/2411:39 amONT - SEA
Nonstop2h 43mAlaska Airlines
Deal found 7/28$157
This Delta deal was found by Cheapflights users on 7/28. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/68:05 amSEA - ONT
Nonstop2h 45mDelta
Sun 9/711:40 amONT - SEA
Nonstop2h 45mDelta
Deal found 7/28$187

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 July 29, 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 9/19

12:30 pm-3:18 pm

Nonstop2h 48m

Ontario

Sun 9/21

8:13 am-11:11 am

Nonstop2h 58m

$138

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Tue 9/16

11:25 am-2:12 pm

Nonstop2h 47m

Ontario

Wed 9/24

11:39 am-2:22 pm

Nonstop2h 43m

$157

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 9/6

7:50 pm-10:42 pm

Nonstop2h 52m

Ontario

Sun 9/7

6:00 am-8:48 am

Nonstop2h 48m

$187

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 9/4

1:05 pm-5:37 pm

1 stop4h 32m

$89

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Fri 8/15

1:42 pm-4:36 pm

Nonstop2h 54m

$92

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Tue 8/26

5:20 am-9:26 am

1 stop4h 06m

$98

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 9/27

5:00 am-11:00 am

1 stop6h 00m

$99

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 9/20

7:55 am-10:44 am

Nonstop2h 49m

$106

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 8/23

8:05 am-10:50 am

Nonstop2h 45m

$109

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/28

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 July 25, 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 July 29, 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 21% 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 July 27, 2025.

Travelers seeking maximum savings on their Seattle to Ontario flight should consider departing on Tuesday afternoons 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.

Weekly flight availability from Seattle to Ontario

Explore weekly flight availability from Seattle to Ontario. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated July 29, 2025.

The most flights from SEA to ONT are scheduled on a Monday (27 on average). You will have fewer flight options on Tuesday, which is when the least amount of flights are scheduled (17 on average).

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 July 29, 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

Crew

8.5

Entertainment

7.1

Boarding

8.1

Food

7.1

Overall

8.0

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

Crew

8.5

Entertainment

7.1

Boarding

8.1

Food

7.1

Overall

8.0

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
4,238 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Crew

8.5

Entertainment

7.1

Boarding

8.1

Food

7.1

Overall

8.0

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
7,977 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Crew

8.5

Entertainment

7.1

Boarding

8.1

Food

7.1

Overall

8.0

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
2,604 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Crew

8.5

Entertainment

7.1

Boarding

8.1

Food

7.1

Overall

8.0

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.
United Airlines
7.4
Good
8,893 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Crew

8.5

Entertainment

7.1

Boarding

8.1

Food

7.1

Overall

8.0

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 20 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 59 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

  • 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 $138 on this airline. Additional options worth looking into are Alaska Airlines and Delta, starting at $157 and $187 round-trip. Frontier is priced at 32% 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 United Airlines. According to our data, you can fly for as low as $89. Users have also found prices from $92 and $98 on Frontier and Alaska 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: Aeromexico (100%), Virgin Atlantic (94%), KLM( 92%).

  • What are the cheapest flights from Seattle to Ontario?

    Looking at all options, your cheapest flight can be booked for $79. While the most popular route (Seattle/Tacoma Intl - Ontario) can be booked for $69 on average our data indicates $192 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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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 July 29, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$64Average$155FlexibilityNo cancel feeOn-time62%
Spirit AirlinesCheapest$72Average$96FlexibilityNo cancel feeOn-time65%
Hawaiian AirlinesCheapest$98Average$247FlexibilityNo cancel feeOn-time85%
DeltaCheapest$117Average$257FlexibilityNo cancel feeOn-timeN/A
Alaska AirlinesCheapest$136Average$270FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$196Average$291FlexibilityNo cancel feeOn-time63%

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