ONT - STL

$67 Find Cheap Flights from Ontario to St. Louis

This is the cheapest one-way flight price found by a KAYAK user in the last 72 hours by searching for a flight from Ontario to St. Louis departing on 4/24. 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 St. Louis

 
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Ontario to St. Louis, 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 Ontario to St. Louis, as well as popular online travel agencies
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Everything you should know

Cheapest round-trip
$163
Overall average: $375
Frontier
Thu 4/9Mon 4/13
ONT - STL • 1 stop
Cheapest one-way
$67
Typical prices: $98-$283
Frontier
Fri 4/24
ONT - STL • 1 stop
Top airlines
Frontier
Cheapest • from $163 (round-trip)
Southwest
Best reviews • 8.0 score
Airline reviews
Airline reviews
+1
+1
Airline reviews
Airline reviews
+1
Nonstop flights
Not available
There are currently no direct flights between Ontario and St. Louis. You'll need at least 1 connection.
Insights
Insights
Insights
Insights
Top layover airports
Las Vegas (LAS)
Cheapest • Avg $300 (round-trip)
Phoenix (PHX)
Shortest trip • 5h 23m (one-way)
Insights
Insights
Insights
Insights
When to book
2 weeks
in advance
Our data shows that travelers who book at least 2 weeks in advance save around 32% compared to booking last minute.
Insights
Insights
Insights
Insights
When to travel
September
Cheapest • 31% price drop
July
Most popular
Good to know
Good to know
+1
+1
Good to know
Good to know
+1
Start a new search
KAYAK searches 100s of sites at once to find you the best travel deals.
We hope you love your trip to St. Louis!
Flight Deals
Booking Insights
Flight Deals

Cheap Flights from Ontario to St. Louis (ONT-STL)

 
Here are some of the best deals found on KAYAK recently from the most popular airlines for round-trip flights from Ontario to St. Louis 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 Ontario to St. Louis

Thu, Apr 9 - Mon, Apr 13
Frontier Logo
6:20 am - 9:48 am
ONT
-
STL
25h 28m
1 stop
Frontier Logo
8:19 pm - 11:55 pm
STL
-
ONT
29h 36m
1 stop
$163Frontier
Thu, Apr 23 - Sun, Apr 26
Frontier Logo
12:59 am - 7:21 pm
ONT
-
STL
16h 22m
1 stop
Frontier Logo
9:55 pm - 8:24 am
STL
-
ONT
12h 29m
1 stop
$190Frontier
Wed, Apr 22 - Mon, Apr 27
Frontier Logo
7:44 pm - 9:00 pm
ONT
-
STL
23h 16m
1 stop
Frontier Logo
3:21 pm - 11:48 pm
STL
-
ONT
10h 27m
1 stop
$191Frontier
Thu, Apr 9 - Mon, Apr 13
Frontier Logo
10:27 pm - 9:48 am
ONT
-
STL
9h 21m
2 stops
Frontier Logo
8:19 pm - 11:55 pm
STL
-
ONT
29h 36m
1 stop
$193Frontier
Thu, Apr 16 - Sat, Apr 18
Frontier Logo
11:47 am - 9:00 pm
ONT
-
STL
7h 13m
1 stop
Frontier Logo
8:17 pm - 7:26 am
STL
-
ONT
13h 09m
1 stop
$197Frontier
Thu, Apr 30 - Sun, May 3
Frontier Logo
12:59 am - 7:21 pm
ONT
-
STL
16h 22m
1 stop
Frontier Logo
9:55 pm - 8:04 pm
STL
-
ONT
24h 09m
1 stop
$201Frontier
Wed, Apr 15 - Sun, Apr 19
Frontier Logo
7:44 pm - 9:00 pm
ONT
-
STL
23h 16m
1 stop
Frontier Logo
9:55 pm - 10:14 am
STL
-
ONT
14h 19m
1 stop
$203Frontier
Fri, Apr 10 - Mon, Apr 13
Frontier Logo
6:20 am - 9:48 am
ONT
-
STL
25h 28m
1 stop
Frontier Logo
8:19 pm - 11:55 pm
STL
-
ONT
29h 36m
1 stop
$207Frontier
Wed, Apr 15 - Sat, Apr 18
Frontier Logo
12:59 am - 7:21 pm
ONT
-
STL
16h 22m
1 stop
Frontier Logo
8:17 pm - 11:56 pm
STL
-
ONT
29h 39m
2 stops
$208Frontier
Sun, Apr 26 - Sat, May 2
Frontier Logo
12:59 am - 7:32 pm
ONT
-
STL
16h 33m
1 stop
Frontier Logo
8:17 pm - 7:26 am
STL
-
ONT
13h 09m
1 stop
$210Frontier
Booking Insights

KAYAK's insights & trends for Ontario to St. Louis flights

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

What is the cheapest month to fly from Ontario to St. Louis?

To calculate monthly average prices, KAYAK takes all prices for each month over the last year for round-trip flights from Ontario to St. Louis, 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 Ontario to St. Louis is September, where tickets cost $241 (return) on average. On the other hand, the most expensive months are December and March, where the average cost of round-trip tickets is $426 and $399 respectively.

How far in advance should I book a flight from Ontario to St. Louis?

To calculate weekly average prices, KAYAK takes all prices for each week before departure over the last year for round-trip flights from Ontario to St. Louis, 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 Ontario to St. Louis, you should book around 2 weeks before departure, which saves you about 32% compared to booking last minute. For the absolute cheapest price, our data suggests you should book 24 weeks before departure.

Good to know

Low seasonOctober
Cheapest flight$67
Best time to beat the crowds with an average 12% drop in price.
Most popular time to fly with an average 7% increase in price.
Flight from Ontario to St. Louis

When to book flights from Ontario to St. Louis

Are your dates flexible? Find out the best times to travel from Ontario to St. Louis 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.

FAQs for booking flights from Ontario to St. Louis

  • What is the cheapest flight from Ontario to St. Louis?

    In the last 3 days, the lowest price for a flight from Ontario to St. Louis was $67 for a one-way ticket and $163 for a round-trip.

  • Do I need a passport to fly between Ontario and St. Louis?

    No

  • Which aircraft models fly most regularly from Ontario to St. Louis?

    We unfortunately don’t have that data for this specific route.

  • Which airline alliances offer flights from Ontario to St. Louis?

    Star Alliance, SkyTeam, and oneworld are the airline alliances operating flights between Ontario and St. Louis, with Star Alliance being the most commonly used for this route.

  • Which is the best airline for flights from Ontario to St. Louis, Southwest or Delta?

    The two airlines most popular with KAYAK users for flights from Ontario to St. Louis are Southwest and Delta. With an average price for the route of $427 and an overall rating of 8.0, Southwest is the most popular choice. Delta is also a great choice for the route, with an average price of $396 and an overall rating of 7.9.

  • How does KAYAK find such low prices on flights from Ontario to St. Louis?

    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 Ontario to St. Louis.

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

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight to St. Louis from Ontario 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 Ontario to St. Louis?

    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 St. Louis with an airline and back to Ontario with another airline. Booking your flights between Ontario and STL can sometimes prove cheaper using this method.

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

    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 St. Louis from Ontario up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

Reviews of the top 5 airlines serving from Ontario to St. Louis

 
See real verified KAYAK customer reviews for airlines flying from Ontario to St. Louis. 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 Ontario to St. Louis? 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.
8.0
SouthwestOverall score based on 4299 reviews
8.1Boarding
7.0Food
7.5Entertainment
8.0Comfort
8.6Crew
Airline reviews

I have not flown Southwest in awhile and had a very pleasant experience. From ticketing to boarding to the flight. The flight left on time and landed ahead of schedule. It won't be so long next time!!

10.0 ExcellentTy&Steph, Feb 2026
CLT - STL
Read more Southwest reviews

I have not flown Southwest in awhile and had a very pleasant experience. From ticketing to boarding to the flight. The flight left on time and landed ahead of schedule. It won't be so long next time!!

The Southwest experience has definitely taken a dive from its early days. You can no longer deferentiate from other airlines. Air travel is too expensive. Southwest is no longer budget friendly. They have lost me as a loyal customer.

Great plane, great attendants,great flight crew,on time. Wonderful flight home..

The charges were ridiculous for an hour flight and the turbulence was very scary.

The seats are now more narrow. I paid for front row the seats in the front are even more narrow than before.

The wifi on the plane is great. The only issue that I have is that I prefer an aisle seat and on my trips this week, I was either in the middle or window. If we can work to secure aisle seating, I will be thrilled. Nice trip.

Everything went smoothly and we even arrived a little bit early.

Great flight but super high price. Glad it was a business trip and not personal

3 hour delay. Had to change plans and was still delayed.

We got exit row seats both flights. Everything was running on time

Flight was delayed by 3-hours and their fix was… complimentary pretzels.

The crew, and fellow passengers, were super gracious and kind. There seemed to be plenty of bin space even though the plane was full. It’s nice to get a glass of wine with dinner in Premiere seating, and there was a lot of food.

Everything I mentioned earlier - the airbus was more comfortable indeed and the experience was further enhanced.

The plane was an older model, so it wasn’t as comfortable as others. The flight attendants were not helpful during onboarding. It was a full flight so there was chaos finding space for baggage.

Awesome! On time flight, early arrival, and a complimentary upgrade!

We departed early and made up time in the air allowing us to arrive 30 minutes early. Capt was incredibly genuine and thanked every passenger for flying with Delta. Completely humble and professional!

Delta One is extraordinary. I fly business when somebody hires me. I just wonder why there is such a chasm between business class and the insanely inhumane and nonsensical coach. The seats are not large enough to fit even my tiny wife. We fly 10% of what we did because we don’t want to pay 5-10 k but for $400 it’s unbearable. It seems like the accountants took over and made stupid decisions. Screw in 20 extra seats and make it so unbearable that people fly 90% less. Just put the damn price up and put some proper chairs in. But business, yay.

Delta’s staff is unmatched. From the gate agents, to the pilots, to the flight attendants… all top of the industry.

The flight was delayed for about 2 hrs. Other than it, it was good.

I am extremely disappointed that delta internal pilot manuals now refer to the Gulf of Mexico as the “gulf of America”. You can bow down to the Orange turd on your own. I will never fly delta again

Women boarding passengers at the gate was absolutely rude and disrespectful of passengers. The flight attendant was absolutely delightful! Smiling and connected with the passengers. So happy. The seats are cramped and uncomfortable but I guess that’s just the way it is Communication regarding flight was excellent

Airport terminal was outdated, flight was on a small jet with no wifi

it was a very short flight so my expectations were low.

Very disappointing given gate agent behavior. Filed a formal complaint with United.

Crew was great (professional, attentive, prompt). Snacks for 4 hrs flight is deplorable.

Flight delayed. WiFi connectivity very poor if not existant. Last minute arrival forced me to run to catch my connection.

Terrible. No customer service, no food, no drinks on a 6 hour premier economy booking.

It was a pretty standard flight... until the almost hour and a half spent on the taxi way. I get that the weather has been poor but the delay had nothing to do with the weather and more to do with a plane with several issues tying up the gate. I get that that happens from time to time but this has been EVERY flight I've been on for the past 5 years and I fly 3 to 5 times a year. This isn't just United... it's American, it's Delta. It's an issue with the entire industry. I work for UPS and packages on a cargo plane get better service than people do these days. Anymore I HATE flying.

The flight crew where really good. Better then the crew from BNE to SFO

left on time, reasonable boarding process arrived early luggage came out quickly

Massimo, flight attendant was very authentic, attentive - wonderful. Food/wrap was just okay.

Experience was great. The best part is the free Wi-Fi connection which helps me to work on the flight

The flight was fine. It's the satellite terminal that supports American eagle flights is what sucks. There is only one food option and everything there is way overpriced. I mean I know it's airport pricing, but it's even crazier than that. I bought a sandwich in a plastic container for $18.

The flight was really crowded. Flight attendants were just ok.

Boarding delayed 20 minutes for no reason, no wifi, in flight entertainment, or snacks / waters?

Flight was delayed for 2 hours, then last minute the change to on time. The satélite location is far and a nightmare to get to.

We flew in first class. The crew did not offer drinks before the flight took off, but they treated us well during the flight. The food was excellent. There was actually too much food served, but it was nice to have all the options.

For a 5 1/2 hour flite i considered the "business class" to be subpar. The seats were just ok, no amenities, really nothing more than a long domestic flight. Frankly disappointed.

It would be nice to have some low carb options in the snacks.

This flight captain and crew were amazing, started ahead of time of departure and reached 30 mins before arrival time. Amazing!

Gate not determined until I got to the airport - hard to plan the trip to the airport.

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

Frontier.. nickel and dime add-ons. Flight late, on time, late again, last minute gate change, arrival gate required a shuttle to the terminal. They sure keep you guessing.. if you like a little chaos and airport anxiety, this is the airline for you!

This is my second time flying with Frontier. My current experience was very favorable. The staff from the gate to the plane was friendly, warm and professional. The food options lacked in my opinion. This area needs some attention in my opinion.

There was no food and no entertainment, so I'm not sure why these are even in the survey, as my understanding is frontier does not ever offer food without a few, not even a snack, and there are no screens so unless the flight safety talk is our entertainment why ask how we liked it?. One of the flight attendants say in the back of the plane as people filed in to their seats, yelling orders about where to put baggage and telling people to hurry up. It was the least professional experience I've ever had on a flight.

It was ok. It was expensive to check 2 bags ($75.00 per bag), and then it took a long time to wait for shuttle to take us from one terminal to the terminal where the plane was taking off at LAX. And all of this for a flight where we had to pay for any food or drink that was not water.

When I wanted to check in 3 hours prior to boarding time, the employees mentioned “a little over an hour delay” so I waited for an hour then I went to go look for food in the terminal and most people from that flight were in the same area looking for food. Finally I decided after food to check to see if it’s anytime closer and now it’s 2 mins until boarding closes?! What are you kidding me? I didn’t receive anything via sms about boarding now nor via email or on the intercom. I luckily made it through, barely, and then there’s no room for my carry on mind you I’m in the very first row so I had to place my purse in one further row back and my carry on sections down. Not sure who pays for better seats to get your stuff placed all over the plane but that was the worst experience I’ve ever had flying with anyone.

This airline sucks. They offer low rates then charge you for everything, the app does not work well, the seats are the most uncomfortable. Maintenance issues on the flight, and you still have to sit through their credit card commercials. People are nice enough but does not make up for overall poor experience.

Cancelled flight after I arrived at airport after 75 min drive and parking. Next flight was 4 days in the future. Had to scramble and buy a much more expensive flight on another carrier.

I liked the turn-style feature at gate 209B at LAX. Very efficient process. The gate staff also made several, clearly directed announcements so I felt very informed.

Everything you need to know for your flight from Ontario to St. Louis

Information on your arrival and departure airports