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$43+ Cheap flights from Ontario to Seattle (ONT - SEA)

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 5/31. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — SEA
Apr 21 — Apr 281
Mon 4/21
Mon 4/28
1 adult, Economy
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Find cheap flights from Ontario to Seattle with Cheapflights

1. Tell us where you want to go

Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”

2. Select your favorite providers

We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.

3. Compare prices and book

Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.

Cheapflights Tip: The best prices from Ontario to Seattle/Tacoma Intl are usually found in January or October, booked 86 days in advance, depart on a Friday or Saturday and return on a Thursday

Cheap flight deals from Ontario to Seattle

Discover tips and strategies to find the most affordable flight options for your journey from Ontario (ONT) to Seattle (SEA). 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 April 16, 2025.

Most accurate provider

Mytrip
3 stars

Most trusted provider

Mytrip
3 stars

Round-trip from

$89
(Frontier)

One-way from

$43
(Flightnetwork)

Popular in

December

Cheapest in

January

Average price

$218

Good round-trip deal

$183 or less

Good one-way deal

$120 or less
Provider with most accurate pricing for Ontario-Seattle/Tacoma Intl flight deals.
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Provider most trusted by Cheapflights users for Ontario-Seattle/Tacoma Intl flights.
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From Ontario to Seattle/Tacoma Intl
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One-way flight from Ontario to Seattle/Tacoma Intl
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Highest demand for flights based on searches. 3% potential increase in price ($5 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease ($6 potential savings vs. average RT price).
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Average for round-trip flights in April 2025
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Price to beat on a round-trip flight from Ontario to Seattle/Tacoma Intl.
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Price to beat on a one-way flight from Ontario to Seattle/Tacoma Intl.
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Find flight deals from Ontario to Seattle

Cheapest flights from Ontario to Seattle
Explore the most affordable flight options available from Ontario to Seattle. Find the lowest fares from popular airlines and budget airlines, with prices last updated on April 16, 2025.

This Frontier deal was found by Cheapflights users on 4/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/3110:03 amONT - SEA
Nonstop3h 00mFrontier
Sat 6/71:50 pmSEA - ONT
Nonstop2h 40mFrontier
Deal found 4/15$89
This Trip.com deal was found by Cheapflights users on 4/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/106:00 amONT - SEA
Nonstop2h 46mMultiple Airlines
Sun 5/116:50 pmSEA - ONT
Nonstop2h 35mMultiple Airlines
Deal found 4/16$132
This Alaska Airlines deal was found by Cheapflights users on 4/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/104:29 pmONT - SEA
Nonstop2h 41mAlaska Airlines
Tue 5/138:13 amSEA - ONT
Nonstop2h 38mAlaska Airlines
Deal found 4/16$157
This Delta deal was found by Cheapflights users on 4/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/106:00 amONT - SEA
Nonstop2h 55mDelta
Sun 5/118:20 amSEA - ONT
Nonstop2h 44mDelta
Deal found 4/16$167
This United Airlines deal was found by Cheapflights users on 4/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/86:00 amONT - SEA
1 stop7h 43mUnited Airlines
Sun 5/115:05 amSEA - ONT
1 stop7h 19mUnited Airlines
Deal found 4/16$172
This Hawaiian Airlines deal was found by Cheapflights users on 4/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Hawaiian Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/144:29 pmONT - SEA
Nonstop2h 41mHawaiian Airlines
Fri 5/168:15 pmSEA - ONT
Nonstop2h 31mHawaiian Airlines
Deal found 4/16$217
This American Airlines deal was found by Cheapflights users on 4/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/61:14 pmONT - SEA
1 stop7h 08mAmerican Airlines
Wed 5/711:40 amSEA - ONT
1 stop6h 43mAmerican Airlines
Deal found 4/15$232
This Southwest deal was found by Cheapflights users on 4/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/305:30 amONT - SEA
2 stops8h 30mSouthwest
Sun 5/45:30 amSEA - ONT
1 stop6h 05mSouthwest
Deal found 4/16$262

Cheapflights 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, Cheapflights users made 2,558,603 searches. Data last updated April 16, 2025.
Use the filters below to find and compare flights from Ontario to Seattle that are best for you.

Fly from

Ontario

Fly to

Seattle

Route

Depart

Return

Price

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 5/31

10:03 am-1:03 pm

Nonstop3h 00m

Seattle/Tacoma Intl

Sat 6/7

1:50 pm-4:30 pm

Nonstop2h 40m

$89

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 5/10

6:00 am-8:46 am

Nonstop2h 46m

Seattle/Tacoma Intl

Sun 5/11

6:50 pm-9:25 pm

Nonstop2h 35m

$132

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 5/10

4:29 pm-7:10 pm

Nonstop2h 41m

Seattle/Tacoma Intl

Tue 5/13

8:13 am-10:51 am

Nonstop2h 38m

$157

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 5/10

6:00 am-8:55 am

Nonstop2h 55m

Seattle/Tacoma Intl

Sun 5/11

8:20 am-11:04 am

Nonstop2h 44m

$167

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Thu 5/8

6:00 am-1:43 pm

1 stop7h 43m

Seattle/Tacoma Intl

Sun 5/11

5:05 am-12:24 pm

1 stop7h 19m

$172

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Wed 5/14

4:29 pm-7:10 pm

Nonstop2h 41m

Seattle/Tacoma Intl

Fri 5/16

8:15 pm-10:46 pm

Nonstop2h 31m

$217

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Tue 5/6

1:14 pm-8:22 pm

1 stop7h 08m

Seattle/Tacoma Intl

Wed 5/7

11:40 am-6:23 pm

1 stop6h 43m

$232

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Wed 4/30

5:30 am-2:00 pm

2 stops8h 30m

Seattle/Tacoma Intl

Sun 5/4

5:30 am-11:35 am

1 stop6h 05m

$262

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Sat 5/31

10:03 am-1:03 pm

Nonstop3h 00m

$43

OntarioSeattle

ONT - SEA

ONTSEA

Ontario

Wed 5/14

11:46 am-2:31 pm

Nonstop2h 45m

$79

Flights are sorted by cheapest round-trip flights first.

Deals found on 4/16

Showing 1-10 of 16 results
1
2

Compare providers for flights from Ontario to Seattle

Provider information is updated monthly. Please note that these providers often have deals for this flight, but the availability may vary on a day-by-day basis on Cheapflights.
Use the table below to compare price accuracy, trust ratings, and cancellation policies for each provider offering flight deals from Ontario to Seattle in April.
ProviderPrice AccuracyTrust Score*
ExpediaPrice Accuracy1 starTrust Score*3 stars
FlightHubPrice Accuracy3 starsTrust Score*2 stars
eDreamsPrice Accuracy3 starsTrust Score*3 stars
CheapflightsfaresPrice Accuracy3 starsTrust Score*2 stars
Kiwi.comPrice Accuracy3 starsTrust Score*3 stars
CheapfaremartPrice Accuracy-Trust Score*1 star
CheapOairPrice Accuracy1 starTrust Score*3 stars
PricelinePrice Accuracy1 starTrust Score*3 stars
MytripPrice Accuracy3 starsTrust Score*3 stars
Justfly.comPrice Accuracy3 starsTrust Score*2 stars

*The Trust Score is based on feedback from users after their booking experience. It measures overall satisfaction, helping us identify issues like hidden fees, problems during the ticketing process, and the quality of customer service. This score is our best indicator of the provider's quality and reliability.

  • Most accurate provider: When it comes to deals on Ontario-Seattle flights, users find the pricing of Mytrip to be most consistent on Cheapflights vs. Mytrip Users can find the same prices on Ontario-Seattle flight deals on Cheapflights vs. Mytrip >95% of the time. Price accuracy is based on data collected from Ontario-Seattle flight searches over the past month and is updated monthly.
  • Most trusted provider: When it comes to deals on Ontario-Seattle flights, Cheapflights users trust Mytrip the most. Mytrip has received a user feedback score of 3 out of 3 stars (3 being the best), meaning they have been trusted the most by Cheapflights users looking for Ontario-Seattle flight deals. Provider user feedback score is based on Cheapflights searches over the past month and is updated monthly.

The best insider tips for Ontario to Seattle flights

Snippets provided in this section are AI-generated based on a summarization of Cheapflights-commissioned articles. The articles are presented as-is, for general informational purposes only, and may not be up-to-date. The opinions contained in the articles are original to the author and reflect their authentic experience, which may vary significantly from the experience of others.
Cheapflights partnered with top experts to bring you the best recommendations for your Ontario to Seattle trip
Airlines
Frontier

Frontier offers extra comfort seats with 32” separation for a fee, ideal for taller passengers.


Frontier's Board First option allows early boarding for carry-on bag purchasers and elite members.

Read more about Frontierby Marisa Garcia
Alaska Airlines

Alaska Airlines offers Wi-Fi for a flat fee, ideal for business travelers needing connectivity.


Alaska's Premium Class offers extra legroom and free cocktails, enhancing comfort on short flights.

Read more about Alaska Airlinesby Robert Schrader
Airports
ONT

ONT offers quick security checks compared to LAX, making it ideal for business travelers seeking efficiency.

Read more about ONTby Bill Fink
SEA

Use the Link light rail for an affordable, 40-minute ride from SEA to downtown Seattle, with ample luggage space.

Read more about SEAby Brandon Schultz
Our travel experts
Marisa Garcia

Marisa Garcia

Expert on Frontier

Marisa Garcia

Marisa Garcia

Marisa knows planes inside and out, spending 16 years working on aircraft in hangars at airports around the world. She is an aviation industry expert, specialized in airline interiors and regulations. Ten years ago, she pivoted to journalism. She shares her insights in leading aviation, travel, and business publications and on her site FlightChic.

Read more
Robert Schrader

Robert Schrader

Expert on Alaska Airlines

Robert Schrader

Robert Schrader

One of the web's original travel bloggers, Robert launched his first site Leave Your Daily Hell in 2009. Since then, he's expanded into destination niche sites (one each for Japan, Thailand and Taiwan), in addition to having written for the inflight magazines of Singapore Airlines and Korean Air. Overall, he's visited nearly 100 countries, and flies business as often as possible.

Read more
Bill Fink

Bill Fink

Expert on ONT

Bill Fink

Bill Fink

Bill is an award-winning travel writer with extensive credits covering airlines and the aviation industry for publications including AARP, AFAR, The Points Guy and Yahoo. Based in Portland, Oregon, Bill has traveled to more than 75 countries - and been late for his flight in most of them. He once achieved top-level frequent flier status for all of American, Delta and United Airlines during a single year.

Read more
Brandon Schultz

Brandon Schultz

Expert on SEA

Brandon Schultz

Brandon Schultz

Brandon Schultz is an award-winning food and travel writer based in New York City. His work has appeared in Forbes, AAA, Thrillist, Travel + Leisure, and The Daily Meal, among many others, and he is the author of 6 books, including 3 cookbooks.

Read more

Best time to book a flight from Ontario to Seattle

Have a flexible travel schedule? Discover the best time to fly to Seattle from Ontario 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 Ontario to Seattle

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

Use this chart to determine the optimal time to book a round-trip flight from Ontario to Seattle. Price data was last updated on April 11, 2025.

To ensure you get the cheapest price possible for a flight from Ontario to Seattle, you should look to book at least 40 days in advance of your intended travel date. The price of your flight may increase if you delay and leave booking until a week or so before departure.

What is the cheapest month to book a flight from Ontario to Seattle?

Currently, January is the cheapest month in which you can book a flight from Ontario to Seattle (average of $238). Flying from Ontario to Seattle in July is currently the most expensive (average of $411). 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 ONT to SEA?

Find hourly flight availability from Ontario to Seattle. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated April 16, 2025.

It’s typically best to fly out from Ontario to Seattle in the morning. Doing so could potentially save you 38% on the flight price compared to flying at noon, which is usually more expensive.

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

Use this chart to determine the cheapest time to fly round-trip from Ontario to Seattle. Price data was last updated on March 30, 2025.

Travelers seeking maximum savings on their Ontario to Seattle flight should consider departing on Friday mornings when fares are most often at their lowest. Sunday at noon flights should be avoided if possible as fares are typically the most expensive at this time.

Weekly flight availability from Ontario to Seattle

Explore weekly flight availability from Ontario to Seattle. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated April 16, 2025.

The most flights from ONT to SEA are scheduled on a Monday (21 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (12 on average).

Rainfall in Seattle by month

Plan your trip to Seattle by taking into account the average rainfall totals by month.

In terms of precipitation, rainfall in Seattle ranges from 0.7 - 6.6 inches per month. November is typically the wettest month, when rainfall can reach 6.6 in. July is typically the driest time to visit Seattle when rainfall is around 0.7 in.

Temperature in Seattle by month

Plan your trip to Seattle by taking into account the average temperature totals by month.

If weather is an important factor for your trip to Seattle, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 66.2 F. Travelers looking to avoid the cold should look outside of December, when temperatures are typically at their lowest (around 41.0 F).

Reviews of airlines servicing Seattle

Get insights into the airlines that provide service to Seattle. 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 Seattle. Reviews last updated April 16, 2025.
Read reviews from past customers who have flown Alaska Airlines, Southwest and Delta from Ontario to Seattle. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
9,876 reviews

Entertainment

7.1

Overall

8.0

Crew

8.5

Comfort

7.9

Boarding

8.2

Food

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
Alaska Airlines
8.0
Very good
9,876 reviews
Alaska Airlines
8.0
Very good
9,876 reviews

Entertainment

7.1

Overall

8.0

Crew

8.5

Comfort

7.9

Boarding

8.2

Food

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
Southwest
8.0
Very good
4,282 reviews
Alaska Airlines
8.0
Very good
9,876 reviews

Entertainment

7.1

Overall

8.0

Crew

8.5

Comfort

7.9

Boarding

8.2

Food

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
Delta
8.0
Very good
7,916 reviews
Alaska Airlines
8.0
Very good
9,876 reviews

Entertainment

7.1

Overall

8.0

Crew

8.5

Comfort

7.9

Boarding

8.2

Food

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
Hawaiian Airlines
7.9
Good
2,380 reviews
Alaska Airlines
8.0
Very good
9,876 reviews

Entertainment

7.1

Overall

8.0

Crew

8.5

Comfort

7.9

Boarding

8.2

Food

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
United Airlines
7.4
Good
8,665 reviews
Alaska Airlines
8.0
Very good
9,876 reviews

Entertainment

7.1

Overall

8.0

Crew

8.5

Comfort

7.9

Boarding

8.2

Food

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them

Related info for your journey

Find useful and relevant information for your journey from Ontario to Seattle. 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 Ontario to Seattle?

    If you wish to fly to Seattle from Ontario, then you need to book flights from Ontario to Seattle/Tacoma Intl. There are 16 flights from Ontario (ONT) to Seattle/Tacoma Intl (SEA) per day to choose from. Flights to Seattle from Ontario are available from 6 different airlines, which means you should have some options if you want to compare airfare deals. 2h 37m is how long a nonstop flight from Ontario to Seattle/Tacoma Intl typically takes.

  • How popular is this Ontario to Seattle flight route?

    The Ontario to Seattle/Tacoma Intl flight path was viewed by 202 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

  • What are the cheapest airlines flying from Ontario to Seattle round-trip?

    Cheapflights users have booked flights from Ontario to Seattle round-trip from $89. Other airlines that can offer you cheap pricing are Alaska Airlines, from $157, and Delta, from $167. You may be able to fly from Ontario to Seattle for 52% less than the average price by searching for these airlines.

  • What are the cheapest airlines to fly from Ontario to Seattle one-way?

    The cheapest airlines for a one-way flight from Ontario to Seattle are Frontier ($43), Alaska Airlines ($79), and Delta ($89).

  • What are the most reliable airlines from Ontario to Seattle?

    Consider KLM (92%), Qatar Airways (91%) or WestJet (91%) when booking your flight. These represent the most reliable airlines when flying from Ontario to Seattle.

  • What are the cheapest flights from Ontario to Seattle?

    While on average a flight from Ontario to Seattle is generally $581, our data shows the cheapest flight currently is $56. When looking at the most popular route, (Ontario - Seattle/Tacoma Intl), you can expect to pay $87 for that flight.

  • Can I find deals for flights from Ontario to Seattle that include hotel bookings?

    Yes. In addition to deals on Ontario to Seattle flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Ontario to Seattle?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Ontario to Seattle.

  • Can I find deals for business class flights from Ontario to Seattle?

    Yes. Cheapflights offers flight deals from Ontario to Seattle 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 Ontario to Seattle?

    Currently, January is the cheapest month in which you can book a flight from Ontario to Seattle (average of $238). Flying from Ontario to Seattle in July is currently the most expensive (average of $411). 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

Traveling to a place near Ontario?

Book flights to Ontario if you plan to visit one of these locations
SeaTac
Tukwila
Tacoma
Renton
Lakewood
Ocean Shores
Lacey
Leavenworth
Federal Way
Olympia
Shoreline
Cle Elum
Centralia
Aberdeen
Kent
Lynnwood
Shelton
Silverdale
Redmond
Issaquah

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Alternative routes for Ontario to Seattle

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Top 6 airlines flying from Ontario to Seattle

Discover the top 6 airlines that operate flights from Ontario to Seattle. 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 2,558,603 searches. Data last updated April 16, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$63Average$140FlexibilityNo cancel feeOn-time62%
Spirit AirlinesCheapest$70Average$130FlexibilityNo cancel feeOn-time65%
Hawaiian AirlinesCheapest$88Average$247FlexibilityNo cancel feeOn-time85%
DeltaCheapest$112Average$245FlexibilityNo cancel feeOn-timeN/A
Alaska AirlinesCheapest$136Average$259FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$150Average$288FlexibilityNo cancel feeOn-time63%

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