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Cheap flights from Seattle to Ontario from C$ 145

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 2/6. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — ONT
22 May — 29 May1
1 adult
1 adult, Economy, 0 bags
Cheapflights Tip: The best prices from Seattle/Tacoma Intl to Ontario are usually found in October or September, booked 75 days in advance, depart on a Friday or Tuesday and return on a Tuesday

Cheap flight deals from Seattle to Ontario

Enter your travel dates to find the best prices.

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 22 April 2026.

Sat 22/811:53 a.m.
SEA
-
ONT
Nonstop2h 46m
Frontier
Sat 29/84:04 p.m.
ONT
-
SEA
Nonstop2h 54m
Frontier
Deal found 18/4C$ 258
Tue 19/512:30 p.m.
SEA
-
ONT
Nonstop2h 39m
Alaska Airlines
Tue 2/64:03 p.m.
ONT
-
SEA
Nonstop2h 49m
Alaska Airlines
Deal found 20/4C$ 269
Thu 7/57:50 p.m.
SEA
-
ONT
1 stop14h 15m
Frontier
Sat 9/510:50 a.m.
ONT
-
SEA
1 stop22h 59m
Frontier
Deal found 20/4C$ 276
Sat 16/59:45 a.m.
SEA
-
ONT
Nonstop2h 50m
Delta
Fri 29/55:50 p.m.
ONT
-
SEA
Nonstop3h 00m
Delta
Deal found 20/4C$ 283
Sat 6/69:45 a.m.
SEA
-
ONT
Nonstop2h 48m
Delta
Mon 8/65:59 p.m.
ONT
-
SEA
Nonstop2h 51m
Delta
Deal found 22/4C$ 284
Sat 23/512:10 p.m.
SEA
-
ONT
1 stop5h 30m
Southwest
Sat 30/54:10 p.m.
ONT
-
SEA
1 stop6h 20m
Southwest
Deal found 20/4C$ 296
Sat 22/811:53 a.m.
SEA
-
ONT
Nonstop2h 46m
Frontier
Mon 31/84:04 p.m.
ONT
-
SEA
Nonstop2h 54m
Frontier
Deal found 18/4C$ 299
Wed 3/66:30 a.m.
SEA
-
ONT
1 stop8h 40m
Southwest
Wed 10/67:20 p.m.
ONT
-
SEA
1 stop5h 20m
Southwest
Deal found 19/4C$ 301
Sat 6/66:30 a.m.
SEA
-
ONT
1 stop7h 10m
Southwest
Tue 9/64:35 p.m.
ONT
-
SEA
2 stops6h 55m
Southwest
Deal found 22/4C$ 303
Tue 12/55:02 a.m.
SEA
-
ONT
1 stop7h 36m
United Airlines
Sat 16/56:59 p.m.
ONT
-
SEA
1 stop6h 13m
United Airlines
Deal found 20/4C$ 306
Wed 3/68:32 a.m.
SEA
-
ONT
Nonstop2h 40m
Alaska Airlines
Sat 6/64:03 p.m.
ONT
-
SEA
Nonstop2h 49m
Alaska Airlines
Deal found 19/4C$ 310
Wed 12/86:25 a.m.
SEA
-
ONT
2 stops7h 10m
Southwest
Wed 12/82:40 p.m.
ONT
-
SEA
1 stop5h 35m
Southwest
Deal found 22/4C$ 311

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 22 April 2026.

Round-trip from

C$ 258

One-way from

C$ 145

Popular in

February

Cheapest in

October

Average price

C$ 406
Frontier
  • Frontier
  • 24/8-29/8
  • Nonstop
  • 5h 40m total
  • Seattle to Ontario
Search Deals
Frontier
  • Frontier
  • 2/6
  • 2 total stops
  • 28h 23m total
  • Seattle to Ontario
Search Deals
Highest demand for flights based on searches. 14% potential increase in price (C$ 80 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 4% potential price decrease (C$ 21 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in April 2026
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 629,999 searches. Data last updated 22 April 2026.
Use the filters below to find and compare flights from Seattle to Ontario that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Wed 12/8

6:25 a.m.-1:35 p.m.

2 stops7h 10m

Ontario

Wed 12/8

2:40 p.m.-8:15 p.m.

1 stop5h 35m

C$ 311

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Wed 13/5

1:04 p.m.-5:17 p.m.

1 stop4h 13m

Ontario

Tue 19/5

7:41 p.m.-10:30 p.m.

Nonstop2h 49m

C$ 337

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Tue 19/5

10:09 a.m.-7:08 p.m.

1 stop8h 59m

Ontario

Tue 26/5

7:41 p.m.-10:30 p.m.

Nonstop2h 49m

C$ 351

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Sat 16/5

8:30 a.m.-11:10 a.m.

Nonstop2h 40m

Ontario

Mon 18/5

4:03 p.m.-6:52 p.m.

Nonstop2h 49m

C$ 372

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 14/5

9:29 p.m.-5:17 p.m.

1 stop19h 48m

Ontario

Tue 19/5

4:03 p.m.-6:52 p.m.

Nonstop2h 49m

C$ 410

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Mon 18/5

8:30 a.m.-11:10 a.m.

Nonstop2h 40m

Ontario

Fri 22/5

7:41 p.m.-10:30 p.m.

Nonstop2h 49m

C$ 426

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 14/5

9:22 p.m.-11:58 p.m.

Nonstop2h 36m

Ontario

Wed 27/5

3:35 p.m.-10:25 p.m.

1 stop6h 50m

C$ 426

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Thu 7/5

8:25 a.m.-11:12 a.m.

Nonstop2h 47m

Ontario

Tue 26/5

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

Nonstop3h 00m

C$ 433
Quickest round-trip

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Fri 15/5

9:22 p.m.-11:58 p.m.

Nonstop2h 36m

Ontario

Mon 18/5

8:11 p.m.-11:00 p.m.

Nonstop2h 49m

C$ 447
Cheapest one-way

SeattleOntario

SEA - ONT

SEAONT

Seattle/Tacoma Intl

Tue 2/6

6:50 a.m.-11:55 a.m.

1 stop5h 05m

C$ 149

Flights are sorted by cheapest round-trip flights first.

Deals found on 17/4

Showing 1-10 of 20 resultsSorted by cheapest first
1
2

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 17 April 2026.

Booking 75 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, October is the cheapest month in which you can book a flight from Seattle to Ontario (average of C$ 255). Flying from Seattle to Ontario in February is currently the most expensive (average of C$ 515). 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 22 April 2026.

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 afternoon could potentially save you up to 44% on airfare.

How much does it cost to fly round-trip from Seattle to Ontario?

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 22 April 2026.
Read reviews from past customers who have flown 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.
Frontier
5.7
Fair
2,982 reviews
Check prices

Entertainment

4.3

Boarding

5.9

Food

4.5

Overall

5.7

Comfort

5.4

Crew

6.6

Reviews

1 / 20
2.0
Mediocre

Prodipto,Mar 2026

PHL - BNA

Delay at the beginning in Philly and then huge delay just sitting on the tarmac after landing, for one hour in Nashville
Frontier
5.7
Fair
2,982 reviews
Frontier
5.7
Fair
2,982 reviews
Check prices

Entertainment

4.3

Boarding

5.9

Food

4.5

Overall

5.7

Comfort

5.4

Crew

6.6

Reviews

1 / 20
2.0
Mediocre

Prodipto,Mar 2026

PHL - BNA

Delay at the beginning in Philly and then huge delay just sitting on the tarmac after landing, for one hour in Nashville

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 36m on average. When it comes time to book airfare, you have a few options: there are 9 outbound flights from Seattle/Tacoma Intl to Ontario offered by 1 airline.

  • How popular is this Seattle to Ontario flight route?

    Within the past month, 9 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$ 337, Southwest can have you in Ontario from Seattle in 4h 13m. Seattle and Ontario are separated by a distance of 1539 km. This flight may include one or multiple stops.

  • What is the cheapest airline to fly from Seattle to Ontario round-trip?

    Cheapflights users have booked flights from Seattle to Ontario round-trip from C$ 233. Frontier is currently priced 34% below the average price you’ll pay for this route.

  • 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: SkyWest Airlines (93%), Delta (93%), Japan Airlines (91%).

  • 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, October is the cheapest month in which you can book a flight from Seattle to Ontario (average of C$ 255). Flying from Seattle to Ontario in February is currently the most expensive (average of C$ 515). 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

Browse thousands of different options on Cheapflights for your next trip

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Top airline flying from Seattle to Ontario

Discover the top airline 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 22 April 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapestC$ 233AverageC$ 333FlexibilityNo cancel feeOn-time62%
Search Frontier 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?

Yes, and it’s super simple to set up. Click the bell icon next to the flight deals above and provide a valid email address to enable Price Alerts. That’s it!

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