What airlines fly to St. Louis?

Southwest, American Airlines and Frontier are the top three most popular airlines that fly to St. Louis from Ontario according to our data. Southwest is the first choice among our users, with 39% of people opting to fly with this airline when traveling to St. Louis. Keep in mind that there are 7 different airlines that fly to St. Louis on a routine basis, so you have a few additional options to choose from.

What is the cheapest airline that flies from Ontario to Lambert-St Louis?

American Airlines, Frontier, and Alaska Airlines are the most popular carriers operating from Ontario to Lambert-St Louis

When did momondo last update prices for flights from Ontario Airport to Lambert-St Louis Airport?

Prices for flights from Ontario Airport to Lambert-St Louis Airport are updated daily.

How many operators does momondo search for flights from Ontario Airport to Lambert-St Louis Airport?

There are 5 operators available for flights from Ontario Airport to Lambert-St Louis Airport as of July 2025.

How old do you have to be to fly from Ontario Airport to Lambert-St Louis Airport?

The minimum age for a child to fly alone is five, but airlines that offer an unaccompanied minor (UNMR) service may have their own age limitations. Flight duration, scheduling, and layovers are among the considerations that may influence age limits. We recommend that you double-check with the airline you are booking with for travel from Ontario Airport to Lambert-St Louis Airport.

What documentation or ID do you need to fly to Lambert-St Louis Airport?

The necessary travel and health documents for your Lambert-St Louis Airport trip may vary depending on your travel plans and individual circumstances. Generally, you should have various documents, such as a national ID card or driver's license and a passport that is valid for six months beyond your scheduled arrival date. We recommend seeking advice from your airline or a trusted third party, such as IATA.

$93 Cheap Flights from Ontario to St. Louis in 2025

Q: What is the typical price of a round-trip flight between Ontario and St. Louis?

Prices are currently low for flights on this route. Typical prices usually range from $230 to $496. The lowest price recently found on this route was $185.

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Find the cheapest flights from Ontario to St. Louis

Round-trip

One-way

Last minute

Cheap round-trip flights

11:15 am - 8:55 pmONT-STL

7h 40m1 stop

2:05 pm - 7:35 pmSTL-ONT

7h 30m1 stop

$185Southwest

Find Deal

sáb., sep. 13 - mié., sep. 17

1:55 pm - 8:55 pmONT-STL

5h 00m1 stop

10:15 am - 5:30 pmSTL-ONT

9h 15m2 stops

$190Southwest

Find Deal

sáb., sep. 13 - mié., sep. 17

12:59 am - 9:11 amONT-STL

6h 12m1 stop

7:29 pm - 11:50 pmSTL-ONT

6h 21m1 stop

$194Frontier

Find Deal

mar., ago. 12 - sáb., ago. 16

10:20 am - 9:53 pmONT-STL

9h 33m2 stops

5:18 am - 11:56 amSTL-ONT

8h 38m2 stops

$195American Airlines

Find Deal

sáb., sep. 13 - mié., sep. 17

6:00 am - 5:34 pmONT-STL

9h 34m1 stop

3:35 pm - 12:03 amSTL-ONT

10h 28m1 stop

$203Alaska Airlines

Find Deal

jue., sep. 18 - lun., sep. 22

12:59 am - 9:11 amONT-STL

6h 12m1 stop

7:29 pm - 11:50 pmSTL-ONT

6h 21m1 stop

$204Frontier

Find Deal

jue., ago. 7 - vie., ago. 15

11:59 pm - 9:00 amONT-STL

7h 01m1 stop

3:53 pm - 9:12 pmSTL-ONT

7h 19m1 stop

$211American Airlines

Find Deal

vie., ago. 15 - lun., ago. 18

12:22 pm - 11:14 pmONT-STL

8h 52m2 stops

3:53 pm - 9:12 pmSTL-ONT

7h 19m1 stop

$216American Airlines

Find Deal

vie., ago. 15 - lun., ago. 18

6:00 am - 5:34 pmONT-STL

9h 34m1 stop

6:33 am - 12:37 pmSTL-ONT

8h 04m1 stop

$239Alaska Airlines

Find Deal

sáb., sep. 27 - sáb., oct. 4

10:00 pm - 8:12 amONT-STL

8h 12m1 stop

7:35 am - 12:14 pmSTL-ONT

6h 39m1 stop

$277Delta

Find Deal

jue., ago. 14 - dom., ago. 17

Alaska Airlines flights from Ontario to St. Louis

Our best Alaska Airlines deals on Ontario to St. Louis flight tickets

Alaska Airlines

Sep 18

ONT6:00 amOntario

9h 34m

1 stop

STL5:34 pmLambert-St Louis

Sep 22

STL3:35 pmLambert-St Louis

10h 28m

1 stop

ONT12:03 amOntario

$203

Find similar

Alaska Airlines

Sep 27

ONT6:00 amOntario

9h 34m

1 stop

STL5:34 pmLambert-St Louis

Oct 4

STL6:33 amLambert-St Louis

8h 04m

1 stop

ONT12:37 pmOntario

$239

Find similar

Alaska Airlines

Jul 22

ONT12:00 pmOntario

9h 59m

1 stop

STL11:59 pmLambert-St Louis

Jul 29

STL3:24 pmLambert-St Louis

10h 51m

1 stop

ONT12:15 amOntario

$431

Find similar

American Airlines flights from Ontario to St. Louis

Our best American Airlines deals on Ontario to St. Louis flight tickets

American Airlines

Sep 13

ONT10:20 amOntario

9h 33m

2 stops

STL9:53 pmLambert-St Louis

Sep 17

STL5:18 amLambert-St Louis

8h 38m

2 stops

ONT11:56 amOntario

$195

Find similar

American Airlines

Aug 15

ONT11:59 pmOntario

7h 01m

1 stop

STL9:00 amLambert-St Louis

Aug 18

STL3:53 pmLambert-St Louis

7h 19m

1 stop

ONT9:12 pmOntario

$211

Find similar

American Airlines

Aug 15

ONT12:22 pmOntario

8h 52m

2 stops

STL11:14 pmLambert-St Louis

Aug 18

STL3:53 pmLambert-St Louis

7h 19m

1 stop

ONT9:12 pmOntario

$216

Find similar

How to get the cheapest flight ticket from Ontario to St. Louis

Look no further. We've gone through all the searches for this route on momondo so you have the important information and insights to find the cheapest flight ticket for your trip

Prices

Airlines

What is the typical price of a round-trip flight between Ontario and St. Louis?

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

In general, August is the cheapest month to fly from Ontario to St. Louis. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $221. The month of September is another great option to travel to St. Louis, with average flight prices from Ontario averaging around $267.

What is the cheapest day to depart on your flight to St. Louis?

The cheapest day to depart on your flight to St. Louis is on a Tuesday when prices can be found for as low as $384. This is often the case because there is less demand to fly during this day of the week. If your travel schedule is flexible, try to avoid departing on a Saturday because tickets tend to average around $447. These prices are subject to change though, so be sure to set up a Price Alert for flights to St. Louis.

What is the cheapest time of day to depart on your flight to St. Louis?

Flying to St. Louis from Ontario in the morning is the least expensive time of day to depart. momondo users have found prices as low as $415 when looking at flights departing in the morning. In the afternoon is when there is more demand to fly to St. Louis, so prices are often more expensive at around $426 per ticket.

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

You are more likely to see cheaper flights to St. Louis from Ontario when booking weeks ahead of your departure date. In general, you can expect to find flights to St. Louis for around $346 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to St. Louis from Ontario for as low as $234 on momondo.

How have Ontario to St. Louis flight prices changed over time?

As of July 2025, prices for Ontario to St. Louis flights are approximately 4% cheaper when compared to flights at the same time last year.

When to book flights from Ontario to St. Louis

Are you open to changing your travel dates? Check out the ideal times to fly from Ontario to St. Louis according to our flight data. Find out which month and days have the cheapest flights.

Estimated round-trip price

Cheap Ontario to St. Louis (ONT to STL) flight deals and tips

Find info about flight duration, direct flights, and airports for your flight from Ontario to St. Louis

Best Price Found	$93
Fastest flight time	5h 00m
Direct flights	None
Airports in St. Louis	1 airport

The best one-way flight to St. Louis from Ontario in the past 72 hours is $93. The best round-trip flight deal from Ontario to St. Louis found on momondo in the last 72 hours is $185.

The fastest flight from Ontario to St. Louis takes 5h 00m

There are no direct flights from Ontario to St. Louis. Popular non-direct route for this connection is Ontario Airport - Lambert-St Louis Airport.

There is 1 airport near St. Louis: Lambert-St Louis (STL)

Search flight deals

How far is Ontario to Lambert-St Louis by plane?
There are 1552.8 mi between Ontario and Lambert-St Louis. 5h 00m is a normal flight duration for this route.
When did momondo last update prices for flights from Ontario Airport to Lambert-St Louis Airport?
Prices for flights from Ontario Airport to Lambert-St Louis Airport are updated daily.
How many operators does momondo search for flights from Ontario Airport to Lambert-St Louis Airport?
There are 5 operators available for flights from Ontario Airport to Lambert-St Louis Airport as of July 2025.
How old do you have to be to fly from Ontario Airport to Lambert-St Louis Airport?
The minimum age for a child to fly alone is five, but airlines that offer an unaccompanied minor (UNMR) service may have their own age limitations. Flight duration, scheduling, and layovers are among the considerations that may influence age limits. We recommend that you double-check with the airline you are booking with for travel from Ontario Airport to Lambert-St Louis Airport.
What documentation or ID do you need to fly to Lambert-St Louis Airport?
The necessary travel and health documents for your Lambert-St Louis Airport trip may vary depending on your travel plans and individual circumstances. Generally, you should have various documents, such as a national ID card or driver's license and a passport that is valid for six months beyond your scheduled arrival date. We recommend seeking advice from your airline or a trusted third party, such as IATA.
What is the most popular airline from Ontario to St. Louis?
momondo data reveals that the most frequently booked airline on the route from Ontario to St. Louis is Frontier, representing 47% of all bookings. The subsequent popular airlines are Southwest at 20%, American Airlines at 19%, and Delta at 9%.

Best airlines flying from Ontario to St. Louis

Compare and see reviews for airlines that fly from Ontario to St. Louis with momondo

Airline	Rating	Free Cancellation	Price
Frontier	PriceFrom $132	Free Cancellation	Rating 5.9 3,271 reviews	Search Frontier flights
Delta	PriceFrom $306	Free Cancellation	Rating 8.0 7,951 reviews	Search Delta flights
United Airlines	PriceFrom $316	Free Cancellation	Rating 7.4 8,846 reviews	Search United Airlines flights
American Airlines	PriceFrom $316	Free Cancellation	Rating 7.2 10,000 reviews	Search American Airlines flights
Southwest	PriceFrom $341	Free Cancellation	Rating 8.0 4,249 reviews	Search Southwest flights

St. Charles

Chesterfield

Hermann

Fairview Heights

Maryland Heights

Florissant

Collinsville

Fenton

Farmington

O'Fallon

St. Peters

Alton

Wentzville

Festus

Glencoe

Clayton

Eureka

Edwardsville

Grafton

Shrewsbury

Why use momondo?

Why should I use momondo to find a flight deal from Ontario to St. Louis?

momondo collates all your flight options in one place and lets you filter them to find the perfect flight from Ontario to St. Louis. momondo saves you time and could save you money on your trip.

Can I find flights from Ontario to St. Louis with flexible booking policies on momondo?

Yes. momondo allows you to filter the results for Ontario to St. Louis flights to just show those with flexible booking policies.

How can momondo help me find flights from Ontario to St. Louis?

Once all potential Ontario to St. Louis flight options are in front of you, momondo lets you sort and filter flights based on preferences such as airline, price and flight times amongst many other options.

I’m not ready to book a flight from Ontario to St. Louis right now. Can momondo alert me if prices change?

If you are not ready to book a flight from Ontario to St. Louis now, use our insights above to find helpful tips or alternatively set up a price alert, where momondo will track prices on flights to St. Louis and let you know when they change.