£88 Cheap Flights from Ontario (ONT) to Seattle (SEA)

View £88 flight on Wed, 20 May 2026Opens in a new window

Flight 1

Popular airlines from Los Angeles - Ontario Intl. Airport (ONT) to Seattle-Tacoma International Airport (SEA)

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Cheap Flights from Ontario (ONT) to Seattle (SEA)

Prices were available within the past 7 days and start at £88 for one-way flights and £146 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Alaska Airlines
Wed, 20 May - Wed, 27 May
ONT
Ontario
SEA
Seattle
£146 Return, found 3 hours ago
£146
Return
found 3 hours ago
Select Alaska Airlines flight, departing Wed, 20 May from Ontario to Seattle, returning Wed, 27 May, priced at £146 found 3 hours ago
Alaska Airlines
Wed, 20 May - Wed, 27 May
ONT
Ontario
SEA
Seattle
£153 Return, found 3 hours ago
£153
Return
found 3 hours ago
Select Alaska Airlines flight, departing Wed, 20 May from Ontario to Seattle, returning Wed, 27 May, priced at £153 found 3 hours ago
Alaska Airlines
Wed, 20 May - Wed, 27 May
ONT
Ontario
SEA
Seattle
£168 Return, found 3 hours ago
£168
Return
found 3 hours ago
Select Alaska Airlines flight, departing Wed, 20 May from Ontario to Seattle, returning Wed, 27 May, priced at £168 found 3 hours ago
Alaska Airlines
Fri, 15 May - Sat, 23 May
ONT
Ontario
SEA
Seattle
£176 Return, found 19 hours ago
£176
Return
found 19 hours ago
Select Alaska Airlines flight, departing Fri, 15 May from Ontario to Seattle, returning Sat, 23 May, priced at £176 found 19 hours ago
Alaska Airlines
Fri, 15 May - Sat, 23 May
ONT
Ontario
SEA
Seattle
£190 Return, found 19 hours ago
£190
Return
found 19 hours ago
Select Alaska Airlines flight, departing Fri, 15 May from Ontario to Seattle, returning Sat, 23 May, priced at £190 found 19 hours ago
Alaska Airlines
Wed, 20 May - Wed, 27 May
ONT
Ontario
SEA
Seattle
£197 Return, found 3 hours ago
£197
Return
found 3 hours ago
Select Alaska Airlines flight, departing Wed, 20 May from Ontario to Seattle, returning Wed, 27 May, priced at £197 found 3 hours ago
Alaska Airlines
Wed, 20 May - Wed, 27 May
ONT
Ontario
SEA
Seattle
£201 Return, found 3 hours ago
£201
Return
found 3 hours ago
Select Alaska Airlines flight, departing Wed, 20 May from Ontario to Seattle, returning Wed, 27 May, priced at £201 found 3 hours ago
Alaska Airlines
Fri, 15 May - Sat, 23 May
ONT
Ontario
SEA
Seattle
£204 Return, found 19 hours ago
£204
Return
found 19 hours ago
Select Alaska Airlines flight, departing Fri, 15 May from Ontario to Seattle, returning Sat, 23 May, priced at £204 found 19 hours ago
Alaska Airlines
Wed, 20 May - Wed, 27 May
ONT
Ontario
SEA
Seattle
£209 Return, found 3 hours ago
£209
Return
found 3 hours ago
Select Alaska Airlines flight, departing Wed, 20 May from Ontario to Seattle, returning Wed, 27 May, priced at £209 found 3 hours ago
Alaska Airlines
Wed, 20 May - Wed, 27 May
ONT
Ontario
SEA
Seattle
£220 Return, found 3 hours ago
£220
Return
found 3 hours ago
Select Alaska Airlines flight, departing Wed, 20 May from Ontario to Seattle, returning Wed, 27 May, priced at £220 found 3 hours ago

Find the cheapest month to fly from Ontario (ONT) to Seattle (SEA)

May is typically the cheapest month to fly

From £75 - £155 per traveller.

Frequently asked questions

How much is a flight from Ontario Airport to Sea-Tac Airport?
If you're travelling between Ontario Airport and Seattle - Tacoma Intl. Airport (SEA), round-trip journeys start from £146. This figure is based on fares quoted within the last 7 days on Expedia for flights departing within the next year, so don't hang about. Book now and save yourself both money and time. Prices and availability are subject to change. Additional terms apply.
Do I need to pay a cancellation fee if I cancel my flight from Los Angeles - Ontario Intl. Airport (ONT) to Sea-Tac Airport?
We understand that things come up unexpectedly, so we've made it as simple as possible for you to cancel your trip online. Just visit the Customer Service Portal and follow the instructions.
How do I find cheap flights from Ontario Airport to Seattle - Tacoma Intl. Airport (SEA) that have flexible change policies?
Many airlines offer the option to reschedule your flight without a change fee. All you pay is the difference between the original flight and the new flight. When you're searching for Los Angeles - Ontario Intl. Airport (ONT) to Seattle - Tacoma Intl. Airport (SEA) flights, you'll see a "no change fees" filter for you to select.
How far is the flight from Los Angeles - Ontario Intl. Airport (ONT) to SEA?
The flight distance from Los Angeles - Ontario Intl. Airport (ONT) to Sea-Tac Airport is 1,550 kilometres. Pack yourself a drink, some snacks and an interesting novel to read. Keep yourself busy in the air and time will zip by.
Which airlines fly direct from Los Angeles - Ontario Intl. Airport (ONT) to Seattle - Tacoma Intl. Airport (SEA)?
Many travellers choose to fly with Alaska Airlines (AS) from Ontario Airport to Seattle - Tacoma Intl. Airport (SEA). This leading airline offers 117 flights monthly, so you can easily find a flight time that works for you. Another carrier operating on this route is Delta Air Lines (DL). You'll have 86 flights every month to choose from.
Are Ontario Airport to Seattle - Tacoma Intl. Airport (SEA) flight tickets cheaper when they're purchased at the last minute?
Last-minute planners can sometimes pick up a bargain, with some super cheap airfares from ONT to Sea-Tac Airport popping up a few weeks prior to the departure date. If you'd rather book ahead of time, Expedia compares and updates all the best flight deals regularly — as early as a year in advance in some cases. It does depend on the carrier though, as not all airlines release prices so far in advance.

Frequently asked questions

How much does a flight from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) cost?
One-way flights typically cost between £150 and £799 and return flights often range between £661 and £1,596. Flight prices vary based on the month and day of the week you want to travel, as well as the airline and how far in advance you book your ticket. Filter your search on Expedia by "Price (lowest to highest)" to see the cheapest fares first, and use the Price Tracking tool to receive alerts when Anaa (AAA) to Toronto, ON (YYZ-Pearson Intl.) ticket fares go up or down.
What is the cheapest month to fly from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
February is typically the cheapest month to fly from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.), with average return fares of approximately £343. This is about 15% lower than the average price throughout the year. February often sees lower prices as it's outside of peak holiday travel seasons, leading to reduced demand. Other cheap months to fly from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) include March and September.
Which airlines fly direct from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
Enter ONT to SEA and your travel dates, then apply the 'Nonstop' filter to see only direct flights.
How do I find cheap flights from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
To find a cheap flight from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.), be flexible with your dates. Traveling outside of peak vacation months and booking a mid-week flight can help you save. Early morning and late night flights are often more affordable, too. Expedia allows you to compare flight times, airlines and routes all in one place to find low fares. You can also set up Price Tracking and receive alerts when fares go up or down.
What is the best airline to fly with from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
The best airline to fly with from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) will differ from traveller to traveller. If you like to fly early, AS offers early morning flights. If price is the most important factor, F9 typically offers the lowest fares. WN offers the most daily flights from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.), which is brilliant if flexibility is what you value most. The best carrier for this journey could also be the one you have a loyalty membership with, as flying with that airline or another airline within the same alliance could help you collect points or enjoy lounge access.
What is the best time to fly from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
The best time to fly from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) is September. This month offers a great balance, as it's both one of the cheapest and most popular times to travel. You can expect return flights to be around £343, and with its popularity, you'll find plenty of flight options to choose from. If you're looking for another good value month, February is also typically cheap, though it might have fewer flight options.
How many flights per day from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
There are approximately 5 nonstop flights per day from Los Angeles - Ontario Intl. (ONT) to Seattle - Tacoma Intl. (SEA). For even more choice, look at flights that include layovers, as there are around 70 connecting flights per day. Some common connection points include Sky Harbor Intl. (PHX), Portland Intl. (PDX), and McCarran Intl. (LAS).
What is the earliest flight from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
The earliest flight from Los Angeles - Ontario Intl. (ONT) to Seattle - Tacoma Intl. (SEA) typically departs at approximately 12:05 AM local time, operated by Frontier Airlines. This is a seasonal service active in May. An early departure like this can help maximise your time at your destination. To compare early flights on Expedia, select the "Early Morning" and "Morning" filters in your search.
What day of the week has the most flights from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
You'll typically find the most flights from Los Angeles - Ontario Intl. (ONT) to Seattle - Tacoma Intl. (SEA) on a Friday, with around 56 flights available. This gives you plenty of options for your travel plans. Major airlines on this route include Southwest Airlines, Alaska Airlines, and American Airlines. Fridays offer notably more flight options compared to other days of the week, making it a great day to travel if you're looking for flexibility.
What are the most popular departure times for flights from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
The most popular departure times for flights from Los Angeles - Ontario Intl. (ONT) to Seattle - Tacoma Intl. (SEA) are in the early morning, from 6am to 9am. About 27% of passengers prefer this time window. Many major carriers, including Southwest Airlines, Alaska Airlines and Delta Air Lines, offer flights during this window. This timing works well for travelers who want to arrive at their destination early in the day, giving them more time to settle in or start their activities.
How long does it take to fly from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
Direct flights from ONT to SEA usually take about 3 hours, traveling roughly 957 miles. If you opt for a connecting flight, expect to add around 5 hours 30 minutes to your journey. Keep in mind that actual flight times can vary due to wind patterns, weather, and air traffic.
Can you fly business or first class from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
Select the "Business class" and "First class" filters when looking for ONT to SEA flights on Expedia. This is the easiest way to compare prices, routes and flight times for your trip.
How do I earn miles on a Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) flight with Expedia?
It's easy to earn miles on a Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) flight when you book with Expedia. Before you confirm your booking, simply select your frequent flyer program and enter your program number. As a member of One Key™, you can also earn OneKeyCash™* on top of your airline miles when you book with Expedia. *Excludes taxes and fees. OneKeyCash is not redeemable for cash and can only be used on Expedia and other participating brands.
What airports do you fly into for Seattle from Los Angeles - Ontario Intl. (ONT)?
If you're planning to travel to Seattle from Los Angeles - Ontario Intl. (ONT), you can fly directly into Seattle - Tacoma Intl. (SEA) Some flights may connect through major hubs like San Francisco Intl. (SFO), Sky Harbor Intl. (PHX), McCarran Intl. (LAS) before reaching Seattle. Compare routes and airports on Expedia to find the best flight options for your travel plans.
Is it cheaper to buy a plane ticket from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) at the last minute?
Typically, booking a last minute flight from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) will be more expensive than booking in advance. As the departure date approaches, there are usually fewer seats available which can drive up the cost. However, if there's some wiggle room with your travel dates and times, you could bag a cheap last-minute fare.
Is it cheaper to book a Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) flight and hotel package?
Securing a Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) flight and hotel package is usually cheaper than booking separately. With Expedia, you can enjoy the ease of organizing your travels all in one place. Select from our extensive range of stays and then add flights, activities and car rentals to your booking. Bundle everything together, and you could save hundreds of dollars.
Can I cancel or change the date of my flight from Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.)?
If you booked your Ontario, CA (ONT-Los Angeles - Ontario Intl.) to Seattle, WA (SEA-Seattle - Tacoma Intl.) flight within the last 24 hours, you may be able to modify or cancel it without any fees. Depending on the airline and the type of ticket you have, additional charges may apply for changes beyond this timeframe. Airline policies and contact information can be found in your itinerary or confirmation email. Or, head to our Customer Service portal if you'd like more information.

Travel information

Origin airport
Los Angeles - Ontario Intl.
Destination airport
Seattle - Tacoma Intl.
Airlines serving
Alaska Airlines
Return price
£145
Distance
1530 km
Average flight time
3 hours 11 mins

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