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Cheap flights from Ontario to Seattle from $89

This is the cheapest one-way flight price found by a momondo user in the last 72 hours by searching for a flight from Ontario to Seattle departing on 12/16. Fares may change, and may not be available for all flights or travel dates. Click the price to refresh the search for this deal.
1 adult
0 bags

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Find the cheapest flights from Ontario to Seattle

Cheap round-trip flights

Frontier Logo
8:02 am - 10:55 amONT-SEA
2h 53mnonstop
Frontier Logo
7:17 pm - 9:58 pmSEA-ONT
2h 41mnonstop
$118Frontier
Find Deal
Fri, Oct 31 - Fri, Nov 7
Frontier Logo
8:43 am - 11:41 amONT-SEA
2h 58mnonstop
Frontier Logo
12:30 pm - 3:18 pmSEA-ONT
2h 48mnonstop
$119Frontier
Find Deal
Fri, Oct 3 - Mon, Oct 6
Frontier Logo
10:30 am - 1:26 pmONT-SEA
2h 56mnonstop
Frontier Logo
8:28 am - 11:08 amSEA-ONT
2h 40mnonstop
$122Frontier
Find Deal
Fri, Oct 24 - Sun, Oct 26
Frontier Logo
12:05 pm - 1:13 pmONT-SEA
25h 08m1 stop
Frontier Logo
7:17 pm - 9:58 pmSEA-ONT
2h 41mnonstop
$123Frontier
Find Deal
Sat, Nov 1 - Sun, Nov 2
Delta Logo
5:50 pm - 8:49 pmONT-SEA
2h 59mnonstop
Delta Logo
2:24 pm - 5:10 pmSEA-ONT
2h 46mnonstop
$133Delta
Find Deal
Thu, Oct 16 - Tue, Oct 21
Delta Logo
5:50 pm - 8:49 pmONT-SEA
2h 59mnonstop
Delta Logo
2:19 pm - 5:09 pmSEA-ONT
2h 50mnonstop
$134Delta
Find Deal
Fri, Nov 7 - Sun, Nov 9
Multiple Airlines Logo
1:31 pm - 4:14 pmONT-SEA
2h 43mnonstop
Multiple Airlines Logo
8:28 am - 11:08 amSEA-ONT
2h 40mnonstop
$146Multiple Airlines
Find Deal
Tue, Oct 7 - Sun, Oct 12
Multiple Airlines Logo
6:03 pm - 11:32 pmONT-SEA
5h 29m1 stop
Multiple Airlines Logo
7:17 pm - 9:58 pmSEA-ONT
2h 41mnonstop
$165Multiple Airlines
Find Deal
Fri, Nov 7 - Sun, Nov 9
Southwest Logo
3:50 pm - 10:45 pmONT-SEA
6h 55m2 stops
Southwest Logo
6:55 am - 1:45 pmSEA-ONT
6h 50m1 stop
$170Southwest
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Tue, Oct 7 - Wed, Oct 15
Alaska Airlines Logo
6:00 am - 8:50 amONT-SEA
2h 50mnonstop
Alaska Airlines Logo
8:22 am - 11:05 amSEA-ONT
2h 43mnonstop
$177Alaska Airlines
Find Deal
Sat, Nov 8 - Tue, Nov 11

Frontier flights from Ontario to Seattle

Our best Frontier deals on Ontario to Seattle flight tickets
Frontier
Oct 31
ONT8:02 amOntario
2h 53m
SEA10:55 amSeattle/Tacoma Intl
Nov 7
SEA7:17 pmSeattle/Tacoma Intl
2h 41m
ONT9:58 pmOntario
$118
Find similar
Frontier
Oct 3
ONT8:43 amOntario
2h 58m
SEA11:41 amSeattle/Tacoma Intl
Oct 6
SEA12:30 pmSeattle/Tacoma Intl
2h 48m
ONT3:18 pmOntario
$119
Find similar
Frontier
Oct 24
ONT10:30 amOntario
2h 56m
SEA1:26 pmSeattle/Tacoma Intl
Oct 26
SEA8:28 amSeattle/Tacoma Intl
2h 40m
ONT11:08 amOntario
$122
Find similar

Delta flights from Ontario to Seattle

Our best Delta deals on Ontario to Seattle flight tickets
Delta
Oct 16
ONT5:50 pmOntario
2h 59m
SEA8:49 pmSeattle/Tacoma Intl
Oct 21
SEA2:24 pmSeattle/Tacoma Intl
2h 46m
ONT5:10 pmOntario
$133
Find similar
Delta
Nov 7
ONT5:50 pmOntario
2h 59m
SEA8:49 pmSeattle/Tacoma Intl
Nov 9
SEA2:19 pmSeattle/Tacoma Intl
2h 50m
ONT5:09 pmOntario
$134
Find similar
Delta
Oct 17
ONT11:48 amOntario
2h 57m
SEA2:45 pmSeattle/Tacoma Intl
Oct 22
SEA5:25 amSeattle/Tacoma Intl
6h 49m
1 stop
ONT12:14 pmOntario
$143
Find similar

momondo Fare Finder

 
Customize your flight search to find flights from Ontario to Seattle 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, momondo users made 832,500 searches. Data last updated September 17, 2025.
Use the filters below to find and compare flights from Ontario to Seattle that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Fri 10/31

8:02 am-10:55 am

Nonstop2h 53m

Seattle/Tacoma Intl

Fri 11/7

7:17 pm-9:58 pm

Nonstop2h 41m

$118

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Fri 10/3

8:43 am-11:41 am

Nonstop2h 58m

Seattle/Tacoma Intl

Mon 10/6

12:30 pm-3:18 pm

Nonstop2h 48m

$119

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Fri 10/24

10:30 am-1:26 pm

Nonstop2h 56m

Seattle/Tacoma Intl

Sun 10/26

8:28 am-11:08 am

Nonstop2h 40m

$122

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 11/1

12:05 pm-1:13 pm

1 stop25h 08m

Seattle/Tacoma Intl

Sun 11/2

7:17 pm-9:58 pm

Nonstop2h 41m

$123

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Thu 10/16

5:50 pm-8:49 pm

Nonstop2h 59m

Seattle/Tacoma Intl

Tue 10/21

2:24 pm-5:10 pm

Nonstop2h 46m

$133

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Fri 11/7

5:50 pm-8:49 pm

Nonstop2h 59m

Seattle/Tacoma Intl

Sun 11/9

2:19 pm-5:09 pm

Nonstop2h 50m

$134

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Tue 10/7

1:31 pm-4:14 pm

Nonstop2h 43m

Seattle/Tacoma Intl

Sun 10/12

8:28 am-11:08 am

Nonstop2h 40m

$146

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Fri 11/7

6:03 pm-11:32 pm

1 stop5h 29m

Seattle/Tacoma Intl

Sun 11/9

7:17 pm-9:58 pm

Nonstop2h 41m

$165

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Tue 10/7

3:50 pm-10:45 pm

2 stops6h 55m

Seattle/Tacoma Intl

Wed 10/15

6:55 am-1:45 pm

1 stop6h 50m

$170

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 11/8

6:00 am-8:50 am

Nonstop2h 50m

Seattle/Tacoma Intl

Tue 11/11

8:22 am-11:05 am

Nonstop2h 43m

$177

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 20 resultsSorted by cheapest first
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See travel insights to Seattle from

How to get the cheapest flight ticket from Ontario to Seattle

Look no further. We've gone through all the searches for this route on momondo so you have the important information and insights to find the cheapest flight ticket for your trip

What is the cheapest month to fly to Seattle?

In general, January is the cheapest month to fly from Ontario to Seattle. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $157. If you don’t want to visit Seattle in January, then you should wait until February to fly from Ontario, when ticket prices are also cheap, with an average price of $176.

What is the cheapest day to depart on your flight to Seattle?

On average, the least expensive day to fly to Seattle from Ontario is on a Friday. momondo users have found tickets for Friday departures for as low as $267. However, this price may fluctuate depending on the airline, the season, and holidays. On the other hand, Sunday is the most expensive day to depart from Ontario because it is more convenient for both business and leisure travelers. As a result, prices tend to be around $348.

What is the cheapest time of day to depart on your flight to Seattle?

Flying to Seattle from Ontario in the afternoon is the least expensive time of day to depart. momondo users have found prices as low as $243 when looking at flights departing in the afternoon. Flights to Seattle are more costly in the morning, with an average ticket price of $322. Departure times in the morning fall within the peak daily travel times, which is why tickets can be more expensive.

What is the cheapest Ontario to Seattle/Tacoma Intl flight route?

Fly from Ontario to Seattle/Tacoma Intl for the best Ontario - Seattle/Tacoma Intl flight prices

How far in advance should I book a flight to Seattle?

You are more likely to see cheaper flights to Seattle from Ontario when booking weeks ahead of your departure date. In general, you can expect to find flights to Seattle for around $204 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Seattle from Ontario for as low as $170 on momondo.

What cabin class options are available on Ontario to Seattle/Tacoma Intl flights?

There are 4 cabin classes available to choose from on Ontario to Seattle/Tacoma Intl flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

Can stopping save me money on Ontario to Seattle flights?

No. A direct flight is the cheapest option for a flight between Ontario to Seattle.

How have Ontario to Seattle flight prices changed over time?

As of September 2025, prices for Ontario to Seattle flights are approximately 3% more expensive when compared to flights at the same time last year.

When to book flights from Ontario to Seattle

Are you open to changing your travel dates? Check out the ideal times to fly from Ontario to Seattle according to our flight data. Find out which month and days have the cheapest flights.
Estimated round-trip price

Cheap Ontario to Seattle (ONT to SEA) flight deals and tips

Find info about flight duration, direct flights, and airports for your flight from Ontario to Seattle

Best Price Found

$124

Fastest flight time

2h 40m

Direct flights

Every day

Airports in Seattle

1 airport
The best one-way flight to Seattle from Ontario in the past 72 hours is $124. The best round-trip flight deal from Ontario to Seattle found on momondo in the last 72 hours is $181.
The fastest flight from Ontario to Seattle takes 2h 40m
Direct flights go from Ontario to Seattle every day.
There is 1 airport near Seattle: Seattle/Tacoma Intl (SEA)
Search flight deals

  • How far is Ontario to Seattle/Tacoma Intl by plane?

    The straight-line distance from Ontario to Seattle/Tacoma Intl is 966.6 mi. By plane, this route typically takes 2h 43m.

  • When did momondo last update prices for flights from Ontario Airport to Seattle/Tacoma Intl Airport?

    Prices for flights from Ontario Airport to Seattle/Tacoma Intl Airport are updated daily.

  • How many operators does momondo search for flights from Ontario Airport to Seattle/Tacoma Intl Airport?

  • How old do you have to be to fly from Ontario Airport to Seattle/Tacoma Intl Airport?

    The minimum age a child must be to fly alone is five but airlines that offer an unaccompanied minor (UNMR) service will have their own age restrictions, including rules around flight length, timings, and stopovers. We always recommend checking with the individual airline you are booking with to travel from Ontario Airport to Seattle/Tacoma Intl Airport.

  • What documentation or ID do you need to fly to Seattle/Tacoma Intl Airport?

    The necessary travel and health documents for your Seattle/Tacoma Intl Airport trip may vary depending on your travel plans and individual circumstances. Generally, you should have various documents, such as a national ID card or driver's license and a passport that is valid for six months beyond your scheduled arrival date. We recommend seeking advice from your airline or a trusted third party, such as IATA.

  • What is the most popular plane model from Ontario to Seattle?

  • What is the most popular airline from Ontario to Seattle?

Best airlines flying from Ontario to Seattle

Compare and see reviews for airlines that fly from Ontario to Seattle with momondo
Airline
Rating
Free Cancellation
Price
FrontierPriceFrom $77Free CancellationRating
5.8
3,173 reviews
Search Frontier flights
Hawaiian AirlinesPriceFrom $98Free CancellationRating
7.8
2,729 reviews
Search Hawaiian Airlines flights
DeltaPriceFrom $117Free CancellationRating
7.9
7,961 reviews
Search Delta flights
Alaska AirlinesPriceFrom $149Free CancellationRating
8.0
10,000 reviews
Search Alaska Airlines flights
SouthwestPriceFrom $150Free CancellationRating
8.0
4,242 reviews
Search Southwest flights

  • Alaska Airlines Flights From Ontario to Seattle

    Alaska Airlines flight deals from Ontario to Seattle start from $149 round-trip. Over the 9 Alaska Airlines flights for this route in a normal week, average airfare is usually $265 round-trip - but some users have found much cheaper deals with momondo.

  • Delta Flights From Ontario to Seattle

    $117 is the best Delta flight deal from Ontario to Seattle found on momondo over the last 72 hours. The average Delta ticket price found was closer to $254, however, with flight time and availability significantly affecting the price. Delta (7.9/10 from 7,961 user reviews) flies into Seattle from Ontario 17 times in an average week so prices can vary.

Traveling to a place near Seattle?

Book flights to Seattle if you plan to visit one of these locations
Leavenworth
Tacoma
SeaTac
Ocean Shores
Renton
Olympia
Lynnwood
Kent
Marysville
Puyallup
Federal Way
Kirkland
Tukwila
Shoreline
Lakewood
Centralia
Fife
Cle Elum
Redmond
Westport

Why use momondo?

Why should I use momondo to find a flight deal from Ontario to Seattle?

momondo collates all your flight options in one place and lets you filter them to find the perfect flight from Ontario to Seattle. momondo saves you time and could save you money on your trip.

Can I find flights from Ontario to Seattle with flexible booking policies on momondo?

Yes. momondo enables you to select and highlight flights to Seattle from Ontario with this policy.

How can momondo help me find flights from Ontario to Seattle?

momondo helps you find the best flight between Ontario and Seattle by providing filters to narrow your choice of flights to those matching your criteria. You can select flights based on numerous factors such as price, departure and landing times, airport and airline.

I’m not ready to book a flight from Ontario to Seattle right now. Can momondo alert me if prices change?

Price alerts on flights to Seattle from Ontario are quick and easy to set up on momondo. Simply perform a search and select the price alert feature. It is as simple as that.

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