SEA - ONT

C$ 171 Find Cheap Flights from Seattle to Ontario

This is the cheapest one-way flight price found by a KAYAK user in the last 72 hours by searching for a flight from Seattle to Ontario departing on 27/8. Fares are subject to change and may not be available on all flights or dates of travel. Click the price to replicate the search for this deal.
1 adult
1 adult, Economy, 0 bags

KAYAK searches hundreds of travel sites at once for deals on flights to Ontario

 
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Seattle to Ontario, as well as popular online travel agencies
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Seattle to Ontario, as well as popular online travel agencies
Travellers love KAYAK
41,299,237 searches in the past 7 days on KAYAK

Save 21% or moreCompare multiple travel sites with one search.

Track pricesNot ready to book? Create a price alert for when prices drop.

Free to useThere are no hidden charges or fees.

Filter your dealsChoose cabin class, free Wi-Fi and more.

Everything you should know

Cheapest round-trip
C$ 289
Typical prices: C$ 397-C$ 220
Frontier
Tue 25/8Sat 29/8
SEA - ONT • Direct
Cheapest one-way flights
C$ 171
Typical prices: C$ 177-C$ 315
United Airlines
Thu 27/8
SEA - ONT • 1 stop
Advice from real travellers
AI-powered summary based on content written by KAYAK users. AI can make mistakes.
SeaTac offers SpotSaver for faster security checks.
Allow extra time for bag drop with Hawaiian Airlines.
User tips
User tips
User tips
User tips
Top airlines
Cheapest • from C$ 289 (round-trip)
Best reviews • 7.9 score
Airline reviews
Airline reviews
+1
+1
Airline reviews
Airline reviews
+1
Direct flights
You can fly direct with Alaska Airlines, Delta, and Frontier. Average duration is 2h 43m
Direct flights
Direct flights
+1
+1
Direct flights
Direct flights
+1
When to book
in advance
Our data shows that travellers who book at least 4 weeks in advance save around 41% compared to booking last minute.
Insights
Insights
Insights
Insights
When to travel
Cheapest • 29% price drop
Most popular
Good to know
Good to know
+1
+1
Good to know
Good to know
+1
Start a new search
KAYAK searches hundreds of sites at once to find you the best travel deals.
We hope you love your trip to Ontario!
Flight Deals
Booking Insights
Flight Deals

Cheap Flights from Seattle to Ontario (SEA-ONT)

 
Here are some of the best deals found on KAYAK recently from the most popular airlines for round-trip flights from Seattle to Ontario that are departing in the next months. While these flights were available on KAYAK in the last 72 hours, prices and availability are subject to change and deals may expire.
Discover the best prices for you by selecting your travel dates on KAYAK.

Recent round-trip flight deals from Seattle to Ontario

Tue, 25 Aug - Sat, 29 Aug
Frontier Logo
11:53 a.m. - 2:39 p.m.
SEA
-
ONT
2h 46mdirect
Frontier Logo
4:04 p.m. - 6:58 p.m.
ONT
-
SEA
2h 54mdirect
C$ 289Frontier
Tue, 25 Aug - Sat, 29 Aug
Frontier Logo
8:13 p.m. - 3:09 p.m.
SEA
-
ONT
18h 56m
1 stop
Frontier Logo
4:04 p.m. - 6:58 p.m.
ONT
-
SEA
2h 54mdirect
C$ 318Frontier
Fri, 25 Sep - Mon, 28 Sep
Delta Logo
7:50 p.m. - 10:40 p.m.
SEA
-
ONT
2h 50mdirect
Delta Logo
6:00 p.m. - 8:50 p.m.
ONT
-
SEA
2h 50mdirect
C$ 328Delta
Thu, 1 Oct - Sun, 4 Oct
Frontier Logo
11:15 a.m. - 2:03 p.m.
SEA
-
ONT
2h 48mdirect
Frontier Logo
5:05 p.m. - 8:01 p.m.
ONT
-
SEA
2h 56mdirect
C$ 332Frontier
Sat, 24 Oct - Sat, 31 Oct
Alaska Airlines Logo
3:25 p.m. - 6:00 p.m.
SEA
-
ONT
2h 35mdirect
Alaska Airlines Logo
7:23 a.m. - 12:05 p.m.
ONT
-
SEA
4h 42m
1 stop
C$ 341Alaska Airlines
Tue, 25 Aug - Sat, 29 Aug
Alaska Airlines Logo
3:50 p.m. - 8:24 p.m.
SEA
-
ONT
4h 34m
1 stop
Alaska Airlines Logo
6:05 p.m. - 10:39 p.m.
ONT
-
SEA
4h 34m
1 stop
C$ 355Alaska Airlines
Thu, 27 Aug - Thu, 27 Aug
Multiple Airlines Logo
8:18 a.m. - 11:04 a.m.
SEA
-
ONT
2h 46mdirect
Multiple Airlines Logo
4:04 p.m. - 6:58 p.m.
ONT
-
SEA
2h 54mdirect
C$ 358Multiple Airlines
Mon, 6 Jul - Fri, 10 Jul
Frontier Logo
8:53 p.m. - 3:14 p.m.
SEA
-
ONT
18h 21m
1 stop
Frontier Logo
3:40 p.m. - 10:39 a.m.
ONT
-
SEA
18h 59m
1 stop
C$ 373Frontier
Fri, 18 Sep - Fri, 18 Sep
Alaska Airlines Logo
11:29 a.m. - 2:16 p.m.
SEA
-
ONT
2h 47mdirect
Alaska Airlines Logo
6:14 p.m. - 10:39 p.m.
ONT
-
SEA
4h 25m
1 stop
C$ 375Alaska Airlines
Thu, 1 Oct - Sun, 4 Oct
Frontier Logo
7:00 a.m. - 11:55 p.m.
SEA
-
ONT
16h 55m
1 stop
Frontier Logo
5:05 p.m. - 8:01 p.m.
ONT
-
SEA
2h 56mdirect
C$ 380Frontier
Booking Insights

KAYAK's insights & trends for Seattle to Ontario flights

Get data-powered insights and trends into flights from Seattle to Ontario to help you find the cheapest flights, the best time to fly and much more.

How much is a round-trip flight from Seattle to Ontario?

This analysis is based on the cheapest round-trip price found on KAYAK in the last 12 months by searching for a flight from Seattle to Ontario departing in August.

What’s the cheapest day of the week to fly from Seattle to Ontario?

The average price of all round-trip flights from Seattle to Ontario clicked on KAYAK for each day over the last 12 months.

When flying from Seattle to Ontario, you should consider leaving on a Saturday and avoid Fridays if you are looking for the best rates. For your return to Seattle, you’ll find the best rates on Wednesdays and the most expensive ones on Saturdays.

What is the cheapest month to fly from Seattle to Ontario?

To calculate monthly average prices, KAYAK takes all prices for each month over the last year for round-trip flights from Seattle to Ontario, removes the top 0.1% to account for outliers, and then takes the median of all values for each month.

The cheapest month for flights from Seattle to Ontario is October, where tickets cost C$ 259 (return) on average. On the other hand, the most expensive months are February and December, where the average cost of round-trip tickets is C$ 521 and C$ 441 respectively.

Can I save money by flying with a layover from Seattle to Ontario?

The average round-trip price for all non-stop flights, flights with one layover, and flights with two layovers for the route found by users searching on KAYAK in the last 2 weeks.

No, with an average price for the route of C$ 438, prices are generally cheapest when you fly direct.

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

To calculate weekly average prices, KAYAK takes all prices for each week before departure over the last year for round-trip flights from Seattle to Ontario, removes the top 0.1% to account for outliers, and then takes the average of all the values for each week.

To get a below average price on the flight from Seattle to Ontario, you should book around 4 weeks before departure, which saves you about 41% compared to booking last minute. For the absolute cheapest price, our data suggests you should book 15 weeks before departure.

Good to know

Low seasonMarch
Cheapest flightC$ 171
Best time to beat the crowds but there is an average 6% increase in price.
Most popular time to fly and prices are also 12% lower on average.
Flight from Seattle to Ontario

When to book flights from Seattle to Ontario

Are your dates flexible? Find out the best times to travel from Seattle to Ontario based on our flight data from the last year. Discover the cheapest month and even day to fly.
Estimated round-trip price
KAYAK looks at all historical flight data for each date to provide a predicted price for one-way trips or round-trips with a duration up to 40 days. While we try to provide actual minimum prices for each date, some prices are predictions and actual prices may differ.

Flights from Seattle to Ontario: the best tips from KAYAK users' own experiences

Insights shared by verified travellers who flew the route from Seattle to Ontario 
Verified travelerFlew with Hawaiian Airlines
SEA
-
ONT
Jun 2025
Make sure to be there on time because the bag drop off can be a little complicated and it takes quite some time to get to the gate.
Verified travelerFlew with Alaska Airlines
SEA
-
ONT
Oct 2024
SeaTac lets you make an appointment to get through security. SpotSaver. No cost. Online.

FAQs for booking flights from Seattle to Ontario

  • What is the cheapest flight from Seattle to Ontario?

    In the last 3 days, the lowest price for a flight from Seattle to Ontario was C$ 171 for a one-way ticket and C$ 289 for a round-trip.

  • Which airports will I be using when flying from Seattle to Ontario?

    Seattle airport is called Seattle/Tacoma Intl and the only airport in Ontario is Ontario.

  • Which airlines offer Wi-Fi service onboard planes from Seattle to Ontario?

    Alaska Airlines, Delta, Hawaiian Airlines, and American Airlines offer inflight Wi-Fi service on the Seattle to Ontario flight route.

  • Which aircraft models fly most regularly from Seattle to Ontario?

    The Boeing 737-800 Passenger/BBJ2 (winglets) is the aircraft model that flies most regularly on the Seattle to Ontario flight route.

  • Which airline alliances offer flights from Seattle to Ontario?

    oneworld is the only airline alliance operating flights between Seattle and Ontario.

  • On which days can I fly direct from Seattle to Ontario?

    There are direct flights from Seattle to Ontario on a daily basis.

  • Which is the best airline for flights from Seattle to Ontario, Alaska Airlines or Frontier?

    The two airlines most popular with KAYAK users for flights from Seattle to Ontario are Alaska Airlines and Frontier. With an average price for the route of C$ 438 and an overall rating of 7.9, Alaska Airlines is the most popular choice. Frontier is also a great choice for the route, with an average price of C$ 337 and an overall rating of 5.6.

  • How does KAYAK find such low prices on flights from Seattle to Ontario?

    KAYAK is a travel search engine. That means we look across the web to find the best prices we can find for our users. With over 2 billion flight queries processed yearly, we are able to display a variety of prices and options on flights from Seattle to Ontario.

  • How does KAYAK's flight Price Forecast tool help me choose the right time to buy my flight ticket from Seattle to Ontario?

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight to Ontario from Seattle is likely to change within 7 days, so travelers know whether to wait or book now.

  • What is the Hacker Fare option on flights from Seattle to Ontario?

    Hacker Fares allow you to combine one-way tickets in order to save you money over a traditional round-trip ticket. You could then fly to Ontario with an airline and back to Seattle with another airline.

  • What is KAYAK's "flexible dates" feature and why should I care when looking for a flight from Seattle to Ontario?

    Sometimes travel dates aren't set in stone. If your preferred travel dates have some wiggle room, flexible dates will show you all the options when flying to Ontario from Seattle up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

KAYAK’s top tips for finding a cheap flight from Seattle to Ontario

  • Looking for a cheap flight? 25% of our users found flights on this route for C$ 320 or less round-trip.

Prefer to fly direct from Seattle to Ontario?

 
Direct data is based off flight results for the next 60 days. Find direct flights from all airlines flying direct from Seattle/Tacoma Intl to Ontario.
Find which airlines fly direct from Seattle/Tacoma Intl Airport to Ontario Airport, which days they fly and book direct flights.

Direct departures

Seattle/Tacoma Intl to Ontario

Monday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Tuesday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Wednesday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Thursday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Friday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Saturday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Sunday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

See more nonstop flights

Direct returns

Ontario to Seattle/Tacoma Intl

Monday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Tuesday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Wednesday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Thursday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Friday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Saturday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

Sunday

Alaska Airlines,Delta,Frontier

Alaska Airlines,Delta, +1 more

See more nonstop flights

Reviews of the top airlines flying from Seattle to Ontario

 
See real verified KAYAK customer reviews for airlines flying from Seattle to Ontario. Airline scores are aggregated from all reviews left by passengers on KAYAK after flying with an airline. KAYAK doesn’t show reviews that are older than 5 years. Learn how KAYAK collects reviews.
Need help choosing which airline to fly with from Seattle to Ontario? KAYAK airline reviews give an overall score for each airline based on loads of factors, including comfort, boarding, in-flight entertainment and more, to make your decision easier. See airline scores according to verified KAYAK customer reviews.
7.9
Alaska AirlinesOverall score based on 12447 reviews
8.1Boarding
8.5Crew
7.8Comfort
7.0Entertainment
7.1Food
Airline reviews

My boarding passes were pulled from my Apple wallet and my 3 family members who were all sitting together in the same row all got put middle seats and were one of the last to board and barely were able to get our bags in the luggage bins.

2.0 MediocreAnonymous, Jun 2026
SEA - SNA
Read more Alaska Airlines reviews

My boarding passes were pulled from my Apple wallet and my 3 family members who were all sitting together in the same row all got put middle seats and were one of the last to board and barely were able to get our bags in the luggage bins.

I was surprised by everything. The cleanliness, the punctuality, the friendliness of the crew… and the Wi-Fi! Please keep up the good work.

I had to cancel this trip due to medical reasons. I took out flight insurance but I was unable to cancel my reservation on either Kayak or Alaska. I need proof that I did not take this flight to get my refund. I have tried for a week and a half together that information from either Kayak or Alaska but so far I have gotten no response. I am very disappointed!

See what I wrote in the previous section. This was a terrible experience. I would like refund.. I even paid an extra $70 for an aisle seat closer to the front to ensure that I got off early enough to catch the next flight. The fact that the plane did not wait, and even left eearlier, knowing that the first flight came in late, and was moved to a terminal three train stops away is appalling. My friend that flew JetBlue, their flight was delayed and came in later and the connecting flight WAITED for them. How is it that JetBlue could do that, and Alaska could not.

Alaska Airlines staff go out of their way to accommodate my fragile musical instrument, every time. They are unlike any other airline. I've experienced this can-do attitude on several flights with different staff, so this must be the culture of their company. I appreciate Alaska!

It was a bumpy flight but the crew was very attentive and made it a safe and enjoyable experience.

i canceled my flight from SEA to SFO, SNA to SEA and received full refund from Alaska Airlines. i am pleased with the customer service.

Departing flight for our weekend trip was cancelled due to weather which meant our return flight was useless. The whole thing was difficult to get support through but Alaska did recover and was able to reimburse us for the flights yesterday. For some reason, Kayak was not kept in the loop, adding to the confusion.

i canceled my return flight package with Alaska Airlines. Customer Service was excellent and assisted me to cancelled both of our reservations and returned the payment in full. that is excellent service and understanding and empathy of the customers' needs. i like Alaska Airlines and recommend AS to everyone.

The flight attendant was friendly and attentive. Although our interaction was brief—- it made a difference. The crew was upfront about turbulence. I like the Maui pretzels.

There weren't enough employees at check in took awhile to get bags checked. There wasn't a wheel chair for me, I was sent to someone who turns out to work for a different airline, if My flight hadn't been delayed I probably would have missed my flight as it was, by the time I arrived at my gate, they started boarding in about 15 minutes. I don't know who took me to my gate, definitely was not the normal people who take passengers to the gate. I'm guessing she may have been in a management position. I wish I knew her name, she went beyond to help me. With that said everyone was kind, and were doing the best they could. So, I choose to say it was an Adventure, stressful start, but good. In the end went well. The situation was not only difficult for passengers but the employee's.

The staff at the check in counter was so rude. Made you feel Incompetent

Frontier scheduled a 40 minute connection in DEN. What they failed to mention was that they “close the doors” 20 mins prior to departure, which means you only have 20 mins. Not enough time. Possibly against DOT regulations. Filing complaint.

Flight was scheduled at 9:40pm. Got delayed to 10 am, the next day. crazy

The bag check, flight check-in, and onboard experience convinced my wife and me that we will actively go out of our way to avoid flying Frontier Airlines in the future. At bag check, we were informed that check-in could only be completed via the Frontier mobile app. Unfortunately, the app was extremely frustrating—sending us through repetitive, confusing loops that repeatedly forced us to decline add-on services with nearly every click. While most airline apps upsell, this one felt intentionally exhausting. As the process dragged on, we became genuinely concerned that my phone battery would die before check-in could be completed. We approached the bag check staff—who were standing together talking—and explained both our frustration and our predicament. They laughed. Later, my wife described the interaction as “gaslighting,” which felt accurate. We were then informed it would cost $25 per person simply to have our boarding passes printed. From that point forward, the tone of the experience was consistently hostile. The bag check employees were condescending and combative, behaving more like bullies than customer service staff. Unfortunately, that same attitude continued onboard. One flight attendant argued with me when I attempted to stow my backpack in the overhead bin. I explained that we had each paid $75 to check our bags specifically so we would not need to use carry-on space and could have adequate legroom. She demanded to see my ticket, pointed out that it said “no carry-on”—which I acknowledged—and I reiterated that this was precisely why we paid to check our bags. Her response was, “I don’t make the rules.” She then walked away, but not before asking if I “truly wanted to fly back to Chicago today?”—an unnecessary and unmistakable threat. It is also worth noting that despite booking our tickets together in the same transaction, we were not seated together. Upon our return to Chicago—where we could once again sit together—we compared onboard experiences. We both remarked on how unhappy the flight attendants appeared and how each of us was separately asked whether we would like to purchase a beverage. We declined. At no point was water mentioned as an option, leaving us with the clear impression that even water came at a cost—or that complimentary water, if available at all, was deliberately left unmentioned. Overall, the experience was shocking and deeply disappointing, but it was also a profound learning experience—one we will not forget and will not repeat. -Steve

Our flight was canceled. I will never use Kayak nor Frontier for travel again. The entire experience was a headache.

Terrible. The canceled my entire flight when I requested a refund for a trip frontier canceled trip one way.

I knew going into this that Frontier, being a low cost carrier, would be pretty bare bones and charge for most extras but this was made up for by the fact that the airplane was a reasonably new Airbus, every employee was great and best of all, Everett Washington is an amazing airport - thanks Frontier for flying there!!!

i was unable to check in the flight. refund requested

I think Frontier was very good at communication. Their app worked very well. Loading was great and the flight was nice and easy.

Everything you need to know for your flight from Seattle to Ontario

Information on your arrival and departure airports