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ONT - STL

$68 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 8/11. 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
0 bags
Fri 7/12
Fri 7/19

Search 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
In the last 7 days travelers have searched 44,148,666 times on KAYAK, and here is why:

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Cheap flight deals 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 and deals for you by selecting your travel dates.
Choose your dates
12:49 am - 9:37 amONT-STL
6h 48m1 stop
7:29 pm - 1:22 pmSTL-ONT
19h 53m1 stop
$138Frontier
Find Deal
Tue, Aug 13 - Tue, Aug 27
12:49 am - 9:37 amONT-STL
6h 48m1 stop
8:00 pm - 11:44 pmSTL-ONT
5h 44m1 stop
$140Frontier
Find Deal
Tue, Aug 13 - Sat, Aug 17
6:45 am - 6:30 pmONT-STL
9h 45m2 stops
11:36 am - 6:07 pmSTL-ONT
8h 31m1 stop
$217American Airlines
Find Deal
Sat, Sep 14 - Tue, Sep 24
6:45 am - 6:09 pmONT-STL
9h 24m2 stops
11:36 am - 6:28 pmSTL-ONT
8h 52m2 stops
$222American Airlines
Find Deal
Sat, Sep 14 - Tue, Sep 24
6:00 am - 4:28 pmONT-STL
8h 28m1 stop
9:05 am - 5:56 pmSTL-ONT
10h 51m2 stops
$307United Airlines
Find Deal
Wed, Aug 14 - Tue, Aug 27
5:00 pm - 12:36 amONT-STL
5h 36m1 stop
7:55 am - 12:15 pmSTL-ONT
6h 20m1 stop
$336Delta
Find Deal
Fri, Sep 13 - Tue, Sep 17
6:20 pm - 4:30 pmONT-STL
20h 10m1 stop
4:54 pm - 9:52 pmSTL-ONT
6h 58m1 stop
$357United Airlines
Find Deal
Mon, Oct 14 - Tue, Oct 29
7:55 pm - 9:29 amONT-STL
11h 34m2 stops
12:23 pm - 5:33 pmSTL-ONT
7h 10m1 stop
Fri, Jul 5 - Mon, Jul 8
11:28 am - 12:36 amONT-STL
11h 08m2 stops
6:59 pm - 11:51 pmSTL-ONT
6h 52m1 stop
$376Delta
Find Deal
Mon, Sep 30 - Thu, Oct 10
11:20 am - 11:59 pmONT-STL
10h 39m2 stops
8:02 pm - 11:56 pmSTL-ONT
5h 54m1 stop
Wed, Jul 17 - Sat, Jul 20

Flights from Ontario to St. Louis - Travel Insights & Trends

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’s the cheapest day of the week to fly from Ontario to St. Louis?

The average price of all flights from Ontario to St. Louis clicked on KAYAK for each day over the last 12 months.
Your flight ticket price will generally be cheaper if you fly to St. Louis on a Saturday and more expensive on a Monday. On your return trip to Ontario, you should consider flying back on a Thursday, and avoid Fridays for better deals.

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 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 January, where tickets cost $376 on average. On the other hand, the most expensive months are July and December, where the average cost of tickets is $467 and $454 respectively.

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

To calculate daily average prices, KAYAK takes all prices for each day before departure over the last year for 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 month.
To get a below average price on the flight from Ontario to St. Louis, you should book around 3 weeks before departure. For the absolute cheapest price, our data suggests you should book 47 days before departure.

Which airlines provide the cheapest flights from Ontario to St. Louis?

The cheapest price for the route for each airline clicked by KAYAK users in the last 72 hours.
In the last 72 hours, the cheapest one-way ticket from Ontario to St. Louis found on KAYAK was with Frontier for $68. Frontier proposed a round-trip connection from $138 and American Airlines from $217.

Good to know

Low season

January

High season

April

Cheapest flight

$68
Best time to beat the crowds with an average 13% drop in price.
Most popular time to fly and prices are also 6% lower on average.
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 $68 for a one-way ticket and $138 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?

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

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

    The two airlines most popular with KAYAK users for flights from Ontario to St. Louis are Delta and United Airlines. With an average price for the route of $357 and an overall rating of 8.0, Delta is the most popular choice. United Airlines is also a great choice for the route, with an average price of $452 and an overall rating of 7.4.

  • 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.

See more FAQs

Top 4 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
DeltaOverall score based on 10000 reviews
8.6Crew
8.0Entertainment
7.9Comfort
8.2Boarding
7.4Food
Airline reviews

There was plenty of overhead room but half of the passengers were told they had to check their carryon bags. My partner and I checked in as early as possible and our seats were split across the aisle.

4.0 OkayBrooke, Jun 2024SFO - MSP
Read more about Delta reviews

There was plenty of overhead room but half of the passengers were told they had to check their carryon bags. My partner and I checked in as early as possible and our seats were split across the aisle.

Flew first class so everything was great. But maybe because the flights were red eye, no meals were served, just chips. I flew Alaska Air 1st class at 9PM (2 hour flight) and they served beef short rib sliders!

There was a loud squeaky sound the whole time we were flying.

On 2 different flights the wifi was horrible and there was no drink or snack service.

I didn’t not like that I could not select my seat and ended up with the worse seat.

The landing was bad and the hostess came two times and i was sleeping but when she served the person that nexts to me I woke up and she didn’t even asked me if I need any drink or snacks two times!!!!

Plane was late because of a mechanical malfunction and the food listed as available was not. Flight attendants seem over worked and under paid. They just done seem happy. And that can be seen in their faces.

Waited 3 hours on a plane to de-ice due to manpower issues. Waited another hour and a half once we landed because of a gate issue. Missed my connections. Created. A total of 13 hours of delay.

There was no FREE wi-fi nor entertainment screens at all.

Great, on time departure, friendly and accommodating crew, great leg room, Smith flight

The entertainment wasn’t playing in the app or online.

Horrible, the flights kept delaying, so it is obvious that we won't be able to make it to the next connection. No easier/real agent on site to help you figure this out. UA agent on other counters refuse to assist you and direct us to use the QR code/call customer service. So inefficient and poor. While technology seems convenient, but it's not the best interest/experience for customers need help while there is active issue need assistance.

Flight was delayed due to the late arrival of the catering truck, which is quite unacceptable. There was a beverage service, but no pretzel, or cookie, or nuts were served in coach.

I had a great flight. Everything went smoothly and the flight arrived early.

On time take off…US cabins look tired and need of refresh!

I paid $380 for my one-way ticket from California to Minnesota. The fair did not include online check-in. I received instructions from their app to check in at a kiosk. At the kiosk, the boarding pass would not print until an actual person came to verify that I had a personal item and not a carry-on item, On the plane, the person next to me was drunk and allowed to continue to order alcohol. United is garbage I’d rather fly spirit.

Do not like the feeling of being in the basic economy. Everyone should feel good no matter what.

Terrible! The plane was old and you are required to connect your own device to their Wi-Fi rather than have entertainment options in the back of the seat in front of you. The Wi-Fi went out during the flight and there was only one plug for the devices every two seats. Three out of five surrounding my family did not work. The seats and spaces under them were so small I could not fit my backpack, which I’ve always brought on flights and fit before no problem. The crew were unpleasant and patronizing.

Last minute gate change nearly caused us to miss our flight. Change was not announced or displayed in the main board at the old gate. Terrible communication. When we landed we had to wait 20 minutes because there was another plane at the assigned gate. Not the crew’s fault, but adding 20 minutes to a 45 minute flight sucked.

Due to one crew member not showing up to work, our flight was significantly delayed causing us to miss our connecting flight in Houston to Mississippi causing us to be delayed by more than 6 hours and missing our event all together. Very disappointing. All because ONE crew member called in sick. United did grant us a $15 meal voucher, which was a small but appreciated concession that I wasn’t able to use because I ordered my lunch and paid for it before applying the concession, and the staff said it was too late to use it. Ugh! We also had a TWO delay coming back from Mississippi, but that was on American Airlines and it was due to weather, so not their fault. Anyway, not at all impressed with United’s handling of our flight and the HUGE disappointment of missing our important family event for our 90 year old mother. All that money and all that stress and emotions for nothing. Having to wait the hour to bring an employee from LAX seemed like something that should not have happened. Why don’t you have a local back-up? Santa Ana is not a little airport in a rural area.

The flight was delayed several times without explanation. The seats were terribly uncomfortable and wifi isn’t included. All these make for a less than ideal flight.

The flights was delayed by hours and it was the firmest landing I have experienced in my life. My back is still sore.

Internet service was erratic. Crew service was poor and slow. My luggage on this non-stop flight was lost and not recovered

Flight was 1/2 hour delayed leaving Phoenix. Otherwise it was an average flight. Flight crew on this trip was very nice.

Horrible - they lied to me about baggage & boarding, even though I specifically spoke to their agents the day before my flight about my issue. When I showed up they did not let me board and stranded me at my airport until I bought a new flight with money I did not have to spend.

The experience was great and much better than the flight going out. of course I was in first class but the service was excellent

Comfort of seats, ease of boarding. Food selection could be better

Food options were limited which is absolutely embarrassing for a Flight of this size The staff did not come around as much and I am not accustomed to such poor service from American Airlines Drinks I believe were limited to soda and water

Crew were attentive and friendly. Flight was smooth and early! I enjoyed the less crowded plane. Thank you!

We are gluten free, there were not any available complimentary gluten free options.

I strongly dislike Frontier. I find them barebones, the seats not particularly comfortable, the nickel and diming is maddening, the app is TERRIBLE - super confusing to navigate, and the last 4 frontier flights I have flown have been on AVERAGE 2 hours late, one ruining a fancy night out in Vegas with reservations made well in advance, which was nodded to with a measly 5000 miles, which translates to almost nothing. At least credit a free checked bag or something.

8 hr delay. had to buy another ticket with another airline

I appreciated the upgrade to free cary-on bag and seat selection at no charge

Flight was delay 9hrs and nothing was provided at airport, had to go and get a room to sleep in, paid for Uber back and fort with no offers until we landed back home a 1hr later for a $75 voucher for a future flight.

Our flight was delayed an hour, then when we got to board our flight finally, we were waiting in our seats for take off for 45 minutes before it was communicated that there was a maintenance issue therefore we waited on the plane for over an hour while that was resolved. We did not get to Phoenix until almost 3 hours after we were originally supposed to. This was the first and last time I will be flying Frontier.

There were 3 leg for the trip and each leg was delayed by 90 minutes or more. The boarding process takes forever with people waiting on the jetway even though most folks do not have carry-on. The whole process is poorly managed.

They cancelled the flight then did nothing to help us rebook. It was awful - I won’t fly with them again

The process of buying the ticket and navigating all the hidden charges that Frontier throws at you was a terrible experience. The actual airport experience and flying was fine.

The truck that was refueling the plane drove away with the hose still connected to the plane and ripped part of the plane off with it

Terrible. Seats are bad and the baggage policy is inconsistent

Book cheap flights from Ontario to St. Louis

Recent one-way flight deals

 
Only flying one-way? Below are some of the best one-way flight deals from Ontario to St. Louis found on KAYAK in the last 72 hours.
8/11Sun
1 stopFrontier
6h 26mONT-STL
$68
8/13Tue
1 stopFrontier
6h 48mONT-STL
$70
8/7Wed
2 stopsAlaska Airlines
14h 40mONT-STL
$159
6/25Tue
1 stopDelta
5h 58mONT-STL
$174
7/1Mon
1 stopDelta
5h 57mONT-STL
$176
7/16Tue
2 stopsAlaska Airlines
14h 59mONT-STL
$183
8/7Wed
2 stopsAmerican Airlines
8h 02mONT-STL
$191
7/1Mon
2 stopsUnited Airlines
15h 52mONT-STL
$302
7/2Tue
2 stopsAmerican Airlines
8h 17mONT-STL
$318
6/21Fri
2 stopsUnited Airlines
17h 51mONT-STL
$362

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Last minute flights from Ontario to St. Louis

Last minute flight, train and bus deals

 
These last-minute flight deals are the cheapest flights found on KAYAK in the last 72 hours for flights from Ontario to St. Louis that are departing in the next 10 days.
6/13Thu
multi-stopFrontier
11h 25mONT-STL
6/20Thu
multi-stopFrontier
23h 39mSTL-ONT
$213
6/16Sun
multi-stopFrontier
6h 30mONT-STL
6/20Thu
multi-stopFrontier
23h 39mSTL-ONT
$233
6/17Mon
multi-stopFrontier
19h 48mONT-STL
6/20Thu
multi-stopFrontier
19h 45mSTL-ONT
$234
6/13Thu
multi-stop
11h 25mONT-STL
6/17Mon
multi-stop
13h 50mSTL-ONT
$648
6/16Sun
multi-stopUnited Airlines
5h 31mONT-STL
6/19Wed
multi-stopUnited Airlines
10h 23mSTL-ONT
$672
6/16Sun
multi-stopUnited Airlines
5h 20mONT-STL
6/18Tue
multi-stopUnited Airlines
9h 06mSTL-ONT
$691
6/14Fri
multi-stopAmerican Airlines
17h 00mONT-STL
6/20Thu
multi-stopAmerican Airlines
6h 04mSTL-ONT
$803
6/14Fri
multi-stopAmerican Airlines
17h 00mONT-STL
6/19Wed
multi-stopAmerican Airlines
10h 53mSTL-ONT
$808
6/16Sun
multi-stopDelta
8h 56mONT-STL
6/19Wed
multi-stopDelta
10h 19mSTL-ONT
$1,064
6/16Sun
multi-stopDelta
5h 58mONT-STL
6/18Tue
multi-stopDelta
10h 19mSTL-ONT
$1,260

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Ontario - St. Louis Flights

Departure:

Ontario (ONT)United States

Destination:

St. Louis (STL)United States

Return flight deals:

St. Louis - Ontario

Cabin classes: