Cheap Flights from Ontario International to Seattle

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Compare Ontario International to Seattle flight deals

Find the cheapest month or even day of the year to fly to Seattle

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Flight deals from Ontario International to Seattle

Looking for a cheap last-minute deal or the best return flight from Ontario International Airport to Seattle? If you want to travel next month, return fares start from $167. Find the lowest prices on one-way and return tickets right here.

Seattle.$149 per passenger.Departing Fri, 25 Sep, returning Fri, 2 Oct.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Fri, 25 Sep, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Fri, 2 Oct, arriving in Ontario International.Price includes taxes and charges.From $149, select.

Seattle.$165 per passenger.Departing Fri, 30 Oct, returning Mon, 2 Nov.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Fri, 30 Oct, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Mon, 2 Nov, arriving in Ontario International.Price includes taxes and charges.From $165, select.

Seattle.$167 per passenger.Departing Fri, 6 Nov, returning Tue, 10 Nov.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Fri, 6 Nov, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Tue, 10 Nov, arriving in Ontario International.Price includes taxes and charges.From $167, select.

Seattle.$167 per passenger.Departing Fri, 23 Oct, returning Mon, 26 Oct.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Fri, 23 Oct, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Mon, 26 Oct, arriving in Ontario International.Price includes taxes and charges.From $167, select.

Seattle.$167 per passenger.Departing Tue, 8 Sep, returning Fri, 18 Sep.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Tue, 8 Sep, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Fri, 18 Sep, arriving in Ontario International.Price includes taxes and charges.From $167, select.

Seattle.$205 per passenger.Departing Sun, 30 Aug, returning Wed, 9 Sep.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Sun, 30 Aug, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Wed, 9 Sep, arriving in Ontario International.Price includes taxes and charges.From $205, select.

Seattle.$216 per passenger.Departing Wed, 26 Aug, returning Thu, 27 Aug.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Wed, 26 Aug, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Thu, 27 Aug, arriving in Ontario International.Price includes taxes and charges.From $216, select.

Seattle.$227 per passenger.Departing Sat, 12 Sep, returning Wed, 4 Nov.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Sat, 12 Sep, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Wed, 4 Nov, arriving in Ontario International.Price includes taxes and charges.From $227, select.

Seattle.$260 per passenger.Departing Thu, 12 Nov, returning Wed, 2 Dec.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Thu, 12 Nov, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Wed, 2 Dec, arriving in Ontario International.Price includes taxes and charges.From $260, select.

Seattle.$310 per passenger.Departing Wed, 2 Dec, returning Mon, 7 Dec.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Wed, 2 Dec, arriving in Seattle / Tacoma International.Inbound direct flight with Frontier Airlines departs from Seattle / Tacoma International on Mon, 7 Dec, arriving in Ontario International.Price includes taxes and charges.From $310, select.

Seattle.$411 per passenger.Departing Mon, 1 Feb, returning Wed, 3 Feb.Return flight with Southwest Airlines.Outbound indirect flight with Southwest Airlines, departs from Ontario International on Mon, 1 Feb, arriving in Seattle / Tacoma International.Inbound indirect flight with Southwest Airlines, departs from Seattle / Tacoma International on Wed, 3 Feb, arriving in Ontario International.Price includes taxes and charges.From $411, select.

Seattle.$411 per passenger.Departing Tue, 19 Jan, returning Tue, 2 Feb.Return flight with Southwest Airlines.Outbound indirect flight with Southwest Airlines, departs from Ontario International on Tue, 19 Jan, arriving in Seattle / Tacoma International.Inbound indirect flight with Southwest Airlines, departs from Seattle / Tacoma International on Tue, 2 Feb, arriving in Ontario International.Price includes taxes and charges.From $411, select.

Seattle.$530 per passenger.Departing Tue, 29 Dec, returning Fri, 1 Jan.Return flight with Southwest Airlines.Outbound indirect flight with Southwest Airlines, departs from Ontario International on Tue, 29 Dec, arriving in Seattle / Tacoma International.Inbound indirect flight with Southwest Airlines, departs from Seattle / Tacoma International on Fri, 1 Jan, arriving in Ontario International.Price includes taxes and charges.From $530, select.

Seattle.$530 per passenger.Departing Thu, 7 Jan, returning Sun, 10 Jan.Return flight with Southwest Airlines.Outbound indirect flight with Southwest Airlines, departs from Ontario International on Thu, 7 Jan, arriving in Seattle / Tacoma International.Inbound indirect flight with Southwest Airlines, departs from Seattle / Tacoma International on Sun, 10 Jan, arriving in Ontario International.Price includes taxes and charges.From $530, select.

Seattle.$539 per passenger.Departing Tue, 3 Nov, returning Tue, 5 Jan.Return flight with Southwest Airlines.Outbound indirect flight with Southwest Airlines, departs from Ontario International on Tue, 3 Nov, arriving in Seattle / Tacoma International.Inbound indirect flight with Southwest Airlines, departs from Seattle / Tacoma International on Tue, 5 Jan, arriving in Ontario International.Price includes taxes and charges.From $539, select.

Seattle.$547 per passenger.Departing Sat, 12 Sep, returning Fri, 8 Jan.Return flight with Southwest Airlines.Outbound indirect flight with Southwest Airlines, departs from Ontario International on Sat, 12 Sep, arriving in Seattle / Tacoma International.Inbound indirect flight with Southwest Airlines, departs from Seattle / Tacoma International on Fri, 8 Jan, arriving in Ontario International.Price includes taxes and charges.From $547, select.

Find the cheapest month to fly from Ontario International to Seattle

We’re always keeping an eye on fares, so you can find the best one in seconds. It looks like Ontario International to Seattle flights are currently cheapest in September.

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Direct flights from Ontario International to Seattle

Alternative Ontario International to Seattle routes

Looking for the cheapest, fastest or easiest route from Ontario International to Seattle? You could fly into the following airports instead.

Ontario to Seattle: Flight information

The things to know before you go.

Cheapest flight found	$149
Cheapest month to fly	September
Average flight time	2 hrs, 52 mins
Most popular airline	Qatar Airways
Average flights per week	199

Finding cheap flights from Ontario International to Seattle: Frequently asked questions

How many airports are there in Seattle?

There are 4 airports in Seattle: Seattle Lake Union SPB, Seattle Boeing Fld, Seattle / Tacoma International, and Paine Field.

How much are return flights from Ontario International to Seattle?

The best price we found for a return flight from Ontario International to Seattle is $149. This is an estimate based on information collected from different airlines and travel providers over the last 4 days and is subject to change and availability.

How long does it take to fly from Ontario International to Seattle?

2 hours and 52 minutes is the average flight time from Ontario International to Seattle.

Which airlines fly direct from Ontario International to Seattle?

Qatar Airways, Alaska Airlines and WestJet fly direct from Ontario International to Seattle.

How many flights are there a week from Ontario International to Seattle?

As of August 2026, there are 203 flights per week flying from Ontario International to Seattle.

When is the cheapest time to fly from Ontario International to Seattle?

The cheapest month to fly from Ontario International to Seattle is usually September.

Which is the cheapest airport to fly into in Seattle?

If you're flying from Ontario International Airport, the cheapest airport near Seattle is Seattle / Tacoma International – which is 19.5 km away from the centre of Seattle. We've found flights into this airport from $149.

Which upcoming date is cheapest to fly from Ontario International Airport to Seattle on?

After crunching the numbers on our flight calendar, we found that it's currently cheapest to fly from Ontario International Airport to Seattle on Friday, 25 September 2026.

Can I get a direct flight from Ontario International Airport to Seattle?

Yes – the average flight time is 2 hours and 52 minutes.

How can I get the best flight deal from Ontario International Airport to Seattle?

We show every price from over 1,200 airlines and travel agents, comparing them all so you don’t have to. If you know you want to fly to Seattle but you’re not ready to book, set up a Price Alert. We’ll track prices for you, and let you know when they rise or fall.

When is the best time to book flights to Seattle?

We crunched all the numbers in our flight calendar and it looks like the cheapest time to book a flight to Seattle is around 40 days in advance, so don’t leave your flight to the last minute.

What’s the weather like in Seattle?

In August, the average temperature is usually around 18°C. August is typically the warmest month in Seattle, when it usually averages around 23°C. You can expect the least rain in July. The coldest month is December, with temperatures averaging 0°C. The rainiest month is November.

Which is the cheapest airline to fly from Ontario International Airport to Seattle with?

Currently, Frontier Airlines offers the cheapest flight tickets to Seattle.

Travelling from Ontario International Airport (ONT) to Seattle: what you need to know

Hop on a direct flight from Ontario International Airport to Seattle and you'll be in the air for an average of 2 hours 45 minutes.
Ontario (the location of Ontario International Airport) and Seattle share the same timezone — UTC-8.
Ontario International Airport (ONT) to Seattle-Tacoma International Airport (SEA) is the most popular route, with 48 weekly departures to pick from. If you prefer starting your day later, the last flight from ONT to SEA is with Alaska Airlines at 19:24. Choose the first departure operated by Delta Air Lines at 05:40 if you want to get on your way earlier.
Leave plenty of time to make your ONT to Seattle flight. A good rule of thumb is to arrive two hours before international departures and an hour ahead for domestic flights.
During popular months such as July, you'll want to get to the airport even earlier. Arrive two hours before a domestic departure and four hours ahead of an international flight whenever you're flying during peak periods in general.
Start your trip at ONT and travel straight to Seattle-Tacoma International Airport (SEA). That's where you can expect to land when searching for Ontario International Airport to Seattle tickets.
Pick from a variety of carriers that offer direct flights from Ontario International Airport to Seattle. Book your seat with one of these:
ONT is about 5 kilometres from central Ontario. If you're ride-sharing, driving or catching a taxi from the centre, it'll take 15 minutes or so to get there, depending on traffic conditions. If you're using public transport, expect the trip time to be around 45 minutes.
Catching an early flight from Ontario International Airport to Seattle? Avoid the last-minute rush to the terminal (and enjoy a little extra shut-eye) by choosing one of these stays near ONT:
Ontario International Airport scores high marks for its on-time performance. 83% of flights that depart ONT arrive at their destination on time.
The address for ONT is 2900 E. Airport Drive.

How to find the cheapest flights from Ontario International Airport (ONT) to Seattle

$83 is currently the lowest price for a one-way Ontario International Airport to Seattle flight. Return plane tickets start from $149. These fares may change based on availability.
To find cheap flights from ONT to Seattle, book as early as you can. Airlines generally offer lower prices when tickets are first released.
Finding cheap tickets from Ontario International Airport to Seattle is more likely if you're flexible with your dates. Use the 'Whole month' search function to access the lowest fares across every month and bag an epic deal.
Never miss a deal on cheap flights from ONT to Seattle by creating a Price Alert. You'll get an email or notification through the app when a lower fare pops up.
Pick your preferred departure and arrival times, airlines and number of stops with our filters. Then, sort the results for your flight from Ontario International Airport to Seattle by 'Fastest,' 'Best' or 'Cheapest.'

Airports in Seattle

Seattle-Tacoma International Airport (SEA)

Seattle-Tacoma International Airport (SEA) is around 23 kilometres from central Seattle. If you're grabbing a taxi or a ride-share, the drive takes about 25 minutes.
Travelling to the centre by public transport typically takes 35 minutes.
Think about booking a hotel close to SEA if you're coming in on a late flight from Ontario International Airport to Seattle. Settle into one of these accommodation options and avoid the hassle of a long transfer:
To get the lowest price, book your ride from Seattle-Tacoma International Airport about one week in advance of your flight from ONT to Seattle.

Seattle Paine Field International Airport (PAE)

Central Seattle is around 40 kilometres from Seattle Paine Field International Airport (PAE). After your flight from Ontario International Airport to Seattle has landed and you've navigated your way to arrivals, expect a drive of about 40 minutes.
If you travel by public transport, the ride to the centre takes 1 hour 30 minutes or so.
You'll find some comfortable places to call home for the night near PAE. Settle in and get cosy after your ONT to Seattle flight at any of these well-located options:
Get your preferred vehicle, not just what's available, by securing your ride from PAE in advance. You'll also avoid paying more than you have to, especially during busy airport times.

King County International Airport (BFI)

King County International Airport (BFI) is about 11 kilometres from central Seattle. It'll take you about 20 minutes to get to the city centre by taxi or ride-share once you've stepped off your flight from Ontario International Airport to Seattle.
The journey will take around 35 minutes on public transport.
Check in to a hotel close to BFI and go from the plane to your bed in a flash. Whether you're coming in on a late ONT to Seattle flight or just want to simplify your travel plans, these stays will have you settling in quickly:
Rental providers sometimes offer promotions on early bookings, so book your ride from BFI in advance of your flight from Ontario International Airport to Seattle. A bit of planning goes a long way for your wallet.

Best time to go to Seattle

December is the quietest month for flights from Ontario International Airport to Seattle, while July is the busiest. Pick the best time to go to Seattle based on whether you prefer a laid-back vibe or a more bustling atmosphere.
Before booking a Ontario International Airport to Seattle plane ticket, think about the weather you're most comfortable in. August is the warmest month in Seattle, with temperatures ranging from 12ºC to 28ºC.
February has average temperatures of between -1ºC and 11ºC. Search for a cheap ticket from ONT to Seattle around that time if you want to travel in cooler conditions.

More about Seattle

Once you've booked your flight from Ontario International Airport to Seattle, choose a hotel that combines comfort with a great location. Make one of these accommodation options your base for exploring Seattle:
All great adventures should include a little sightseeing. Pike Place Market, Space Needle and Seattle Skyline are must-do's during your Seattle adventure.

Explore more of the United States

Seattle will leave a lasting impression, but there are so many other corners of the United States just waiting to be explored. Around 241 kilometres south of Seattle, a visit to Portland will fill your itinerary to the brim. Check out popular attractions like Portland Japanese Garden, Peninsula Park Rose Garden and Beyond Van Gogh Portland.
Around 370 kilometres east of Seattle, Spokane is another favourite stop in the United States. Experience major highlights starting with Riverside State Park, Spokane Falls (Upper Falls) and Cathedral of Our Lady of Lourdes.