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Cheap flights from Seattle to Ontario from C$ 119

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 6/11. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — ONT
11 Oct — 18 Oct1
1 adult
1 adult, Economy

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 Monday or Thursday 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 11 September 2025.

Round-trip from

C$ 164

One-way from

C$ 119

Popular in

December

Cheapest in

September

Average price

C$ 213

Good round-trip deal

C$ 260 or less

Good one-way deal

C$ 286 or less
Frontier
  • Frontier
  • 10/10-13/10
  • Nonstop
  • 5h 36m total
  • Seattle to Ontario
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Frontier
  • Frontier
  • 6/11
  • 1 total stop
  • 12h 00m total
  • Seattle to Ontario
Search Deals
Highest demand for flights based on searches. 5% potential increase in price (C$ 21 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease (C$ 11 potential savings vs. average RT price).
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Average for round-trip flights in September 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 11 September 2025.

Fri 10/108:28 a.m.SEA - ONT
Nonstop2h 40mFrontier
Mon 13/1010:30 a.m.ONT - SEA
Nonstop2h 56mFrontier
Deal found 11/9C$ 164
Wed 8/106:15 a.m.SEA - ONT
1 stop4h 00mSouthwest
Wed 15/108:40 a.m.ONT - SEA
1 stop7h 25mSouthwest
Deal found 10/9C$ 172
Sat 25/106:15 a.m.SEA - ONT
1 stop4h 00mSouthwest
Wed 5/1111:10 a.m.ONT - SEA
1 stop5h 20mSouthwest
Deal found 11/9C$ 182
Wed 5/1112:58 p.m.SEA - ONT
1 stop10h 52mFrontier
Thu 13/116:00 a.m.ONT - SEA
1 stop12h 32mFrontier
Deal found 10/9C$ 200
Wed 8/106:15 a.m.SEA - ONT
1 stop4h 00mSouthwest
Thu 16/106:30 p.m.ONT - SEA
1 stop4h 35mSouthwest
Deal found 10/9C$ 201
Sat 27/97:00 a.m.SEA - ONT
1 stop12h 54mFrontier
Sat 11/107:04 a.m.ONT - SEA
1 stop24h 29mFrontier
Deal found 10/9C$ 206
Thu 9/108:05 a.m.SEA - ONT
1 stop8h 30mSouthwest
Tue 14/106:00 a.m.ONT - SEA
1 stop4h 40mSouthwest
Deal found 10/9C$ 209
Fri 10/109:25 p.m.SEA - ONT
Nonstop2h 38mMultiple Airlines
Mon 13/1010:30 a.m.ONT - SEA
Nonstop2h 56mMultiple Airlines
Deal found 11/9C$ 219
Sat 25/109:25 p.m.SEA - ONT
Nonstop2h 38mMultiple Airlines
Sun 26/1010:30 a.m.ONT - SEA
Nonstop2h 56mMultiple Airlines
Deal found 10/9C$ 220
Sat 11/106:15 a.m.SEA - ONT
1 stop4h 00mSouthwest
Tue 14/104:35 p.m.ONT - SEA
1 stop6h 10mSouthwest
Deal found 11/9C$ 222
Thu 9/101:02 p.m.SEA - ONT
1 stop10h 48mFrontier
Mon 13/1010:30 a.m.ONT - SEA
Nonstop2h 56mFrontier
Deal found 11/9C$ 226

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 629,999 searches. Data last updated 11 September 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

Wed 8/10

6:15 a.m.-10:15 a.m.

1 stop4h 00m

Ontario

Tue 14/10

4:35 p.m.-10:45 p.m.

1 stop6h 10m

C$ 172

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Wed 8/10

6:15 a.m.-10:15 a.m.

1 stop4h 00m

Ontario

Wed 15/10

8:40 a.m.-4:05 p.m.

1 stop7h 25m

C$ 172

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 4/12

6:15 a.m.-10:35 a.m.

1 stop4h 20m

Ontario

Mon 8/12

3:15 p.m.-7:45 p.m.

1 stop4h 30m

C$ 231

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 11/10

7:05 a.m.-6:35 p.m.

1 stop11h 30m

Ontario

Sat 18/10

4:55 p.m.-10:45 p.m.

1 stop5h 50m

C$ 233

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 11/10

8:15 a.m.-11:08 a.m.

Nonstop2h 53m

Ontario

Wed 22/10

5:50 p.m.-8:49 p.m.

Nonstop2h 59m

C$ 245

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 11/10

9:25 p.m.-12:03 a.m.

Nonstop2h 38m

Ontario

Tue 21/10

7:43 p.m.-10:30 p.m.

Nonstop2h 47m

C$ 245

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Wed 5/11

8:22 a.m.-11:05 a.m.

Nonstop2h 43m

Ontario

Wed 12/11

6:00 a.m.-8:50 a.m.

Nonstop2h 50m

C$ 245

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 11/10

8:15 a.m.-11:08 a.m.

Nonstop2h 53m

Ontario

Sat 25/10

11:48 a.m.-2:45 p.m.

Nonstop2h 57m

C$ 245

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Wed 18/2

3:45 p.m.-6:17 p.m.

Nonstop2h 32m

Ontario

Wed 25/2

6:55 p.m.-9:44 p.m.

Nonstop2h 49m

C$ 245

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Tue 14/10

9:25 p.m.-12:03 a.m.

Nonstop2h 38m

Ontario

Tue 21/10

1:31 p.m.-4:14 p.m.

Nonstop2h 43m

C$ 245

Flights are sorted by cheapest round-trip flights first.

Deals found on 11/9

Showing 1-10 of 21 results
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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 29 August 2025.

Booking 72 days in advance of your planned departure date is, on average, the best time to get cheap flights from Seattle to Ontario. The general trend is that the closer you book to the departure date, the more expensive your flight will be.

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

Currently, September is the cheapest month in which you can book a flight from Seattle to Ontario (average of C$ 290). Flying from Seattle to Ontario in December is currently the most expensive (average of C$ 461). 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 11 September 2025.

One of the essential ways to save on airfare from Seattle to Ontario is to remain as flexible as possible. Flights that are at noon tend to be the most expensive. A flight in the morning could potentially save you up to 24% on airfare.

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 11 September 2025.
Read reviews from past customers who have flown Alaska Airlines and Frontier from Seattle to Ontario. Users can see the overall rating for each airline as well as how each is rated in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
10,000 reviews
Check prices

Comfort

7.8

Overall

8.0

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.0

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
Check prices

Comfort

7.8

Overall

8.0

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.0

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
3,177 reviews
Alaska Airlines
8.0
Very good
10,000 reviews
Check prices

Comfort

7.8

Overall

8.0

Boarding

8.1

Food

7.1

Crew

8.5

Entertainment

7.0

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?

    To fly from Seattle to Ontario, you need to book a flight from Seattle/Tacoma Intl (SEA) to Ontario (ONT). Nonstop flights to Ontario from Seattle/Tacoma Intl take 2h 37m on average. When it comes time to book airfare, you have a few options: there are 14 outbound flights from Seattle/Tacoma Intl to Ontario offered by 2 different airlines.

  • How popular is this Seattle to Ontario flight route?

    Within the past month, 19 users have taken a look at flights from Seattle/Tacoma Intl to Ontario.

  • How long is the flight from Seattle to Ontario?

    For as low as C$ 172, Southwest can have you in Ontario from Seattle in 4h. Seattle and Ontario are separated by a distance of 1539 km.

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

    Cheapflights users have booked flights from Seattle to Ontario round-trip from C$ 97. Another airline that can offer you cheap pricing is Alaska Airlines. Frontier is currently priced 66% below the average price you’ll pay for this route.

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

    C$ 123 is the cheapest one-way deal found within the past few days, from Southwest. You may also be able to find cheap deals on Alaska Airlines and Delta, with prices starting from C$ 151 and C$ 151, respectively.

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

    Looking for the most reliable airlines to get you to your destination on time? Our data shows these are most likely to get you from Seattle to Ontario on time: Scandinavian Airlines (93%), Delta (91%), Virgin Atlantic (90%).

  • What are the cheapest flights from Seattle to Ontario?

    Looking for the cheapest flight from Seattle to Ontario? While on average our users pay C$ 288, our data indicates the cheapest price to be C$ 138. The most popular route (Seattle/Tacoma Intl - Ontario), is priced around C$ 240.

  • 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, September is the cheapest month in which you can book a flight from Seattle to Ontario (average of C$ 290). Flying from Seattle to Ontario in December is currently the most expensive (average of C$ 461). 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 2 airlines flying from Seattle to Ontario

Discover the top 2 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 629,999 searches. Data last updated 11 September 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapestC$ 97AverageC$ 260FlexibilityNo cancel feeOn-time62%
Search Frontier flights
Alaska AirlinesCheapestC$ 216AverageC$ 307FlexibilityNo cancel feeOn-time75%
Search Alaska Airlines flights

Fly with Cheapflights

Find the best flight deals on Cheapflights, where travelers can enjoy low prices and a wide availability of flights to their desired destinations.

How does Cheapflights help users find flights from Seattle to Ontario?

When you search for this flight from Seattle to Ontario, Cheapflights searches on 900+ travel sites to save you time finding great flight deals online. Additionally, we offer filter features so you can choose a preferred cabin class or airline, see different price ranges, and much more so you can book the flight for you.

Why should you use Cheapflights to find cheap flight tickets from Seattle to Ontario?

It’s simple! Cheapflights, which is free to use for everyone, saves millions of users time and money every year by helping them find the cheapest and most suitable flights from Seattle to Ontario.

Can Cheapflights find flights from Seattle to Ontario with no change fees?

Yes! Cheapflights helps users easily find flights from Seattle to Ontario with no change fees.

Can Cheapflights notify me if prices for flights from Seattle to Ontario become cheaper?

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