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Cheap flights from St. Louis to Los Angeles from $71

This is the cheapest one-way flight price found by a momondo user in the last 72 hours by searching for a flight from St. Louis to Los Angeles departing on 9/3. Fares may change, and may not be available for all flights or travel dates. Click the price to refresh the search for this deal.
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Find the cheapest flights from St. Louis to Los Angeles (STL-ONT)

Cheap round-trip flights

Frontier Logo
7:55 pm - 7:54 pmSTL-ONT
25h 59m1 stop
Frontier Logo
8:59 pm - 9:06 amONT-STL
10h 07m1 stop
$142Frontier
Find Deal
Mon, Sep 22 - Tue, Sep 30
Frontier Logo
2:38 pm - 8:56 pmSTL-ONT
8h 18m1 stop
Frontier Logo
8:59 pm - 9:06 amONT-STL
10h 07m1 stop
$143Frontier
Find Deal
Mon, Sep 8 - Fri, Sep 12
Frontier Logo
10:49 am - 3:29 pmSTL-ONT
6h 40m1 stop
Frontier Logo
8:59 pm - 9:06 amONT-STL
10h 07m1 stop
$144Frontier
Find Deal
Thu, Sep 25 - Sat, Sep 27
Logo
7:00 am - 3:17 pmSTL-ONT
10h 17m1 stop
Logo
6:53 am - 9:07 amONT-STL
24h 14m1 stop
$281
Find Deal
Sat, Nov 1 - Sun, Nov 9
Delta Logo
6:50 am - 12:14 pmSTL-ONT
7h 24m1 stop
Delta Logo
6:00 am - 1:39 pmONT-STL
5h 39m1 stop
$287Delta
Find Deal
Wed, Oct 8 - Wed, Oct 22
Delta Logo
1:26 pm - 7:15 pmSTL-ONT
7h 49m1 stop
Delta Logo
9:50 am - 6:40 pmONT-STL
6h 50m1 stop
$297Delta
Find Deal
Sat, Oct 4 - Wed, Oct 22
American Airlines Logo
5:18 am - 10:03 amSTL-ONT
6h 45m1 stop
American Airlines Logo
1:10 pm - 10:50 pmONT-STL
7h 40m2 stops
$298American Airlines
Find Deal
Tue, Sep 16 - Tue, Sep 30
American Airlines Logo
8:50 am - 4:05 pmSTL-ONT
9h 15m2 stops
American Airlines Logo
1:10 pm - 10:50 pmONT-STL
7h 40m2 stops
$303American Airlines
Find Deal
Tue, Sep 16 - Tue, Sep 30
Alaska Airlines Logo
3:35 pm - 12:03 amSTL-ONT
10h 28m1 stop
Alaska Airlines Logo
1:31 pm - 12:03 amONT-STL
8h 32m1 stop
$322Alaska Airlines
Find Deal
Fri, Oct 3 - Tue, Oct 21
Alaska Airlines Logo
2:55 pm - 10:37 pmSTL-ONT
9h 42m1 stop
Alaska Airlines Logo
6:55 pm - 1:52 pmONT-STL
16h 57m1 stop
$326Alaska Airlines
Find Deal
Sat, Feb 7 - Wed, Feb 11

Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Sep 22
STL7:55 pmLambert-St Louis
25h 59m
1 stop
ONT7:54 pmOntario
Sep 30
ONT8:59 pmOntario
10h 07m
1 stop
STL9:06 amLambert-St Louis
$142
Find similar
Frontier
Sep 8
STL2:38 pmLambert-St Louis
8h 18m
1 stop
ONT8:56 pmOntario
Sep 12
ONT8:59 pmOntario
10h 07m
1 stop
STL9:06 amLambert-St Louis
$143
Find similar
Frontier
Sep 25
STL10:49 amLambert-St Louis
6h 40m
1 stop
ONT3:29 pmOntario
Sep 27
ONT8:59 pmOntario
10h 07m
1 stop
STL9:06 amLambert-St Louis
$144
Find similar

American Airlines flights from St. Louis to Ontario

Our best American Airlines deals on St. Louis to Ontario flight tickets
American Airlines
Sep 16
STL5:18 amLambert-St Louis
6h 45m
1 stop
ONT10:03 amOntario
Sep 30
ONT1:10 pmOntario
7h 40m
2 stops
STL10:50 pmLambert-St Louis
$298
Find similar
American Airlines
Sep 16
STL8:50 amLambert-St Louis
9h 15m
2 stops
ONT4:05 pmOntario
Sep 30
ONT1:10 pmOntario
7h 40m
2 stops
STL10:50 pmLambert-St Louis
$303
Find similar
American Airlines
Dec 9
STL7:00 amLambert-St Louis
11h 01m
2 stops
ONT4:01 pmOntario
Dec 13
ONT6:17 amOntario
5h 34m
1 stop
STL1:51 pmLambert-St Louis
$312
Find similar

momondo Fare Finder

 
Customize your flight search to find flights from St. Louis to Ontario 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, momondo users made 832,500 searches. Data last updated August 28, 2025.
Use the filters below to find and compare flights from St. Louis to Ontario that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 9/22

7:55 pm-7:54 pm

1 stop25h 59m

Ontario

Tue 9/30

8:59 pm-9:06 am

1 stop10h 07m

$142

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 9/8

2:38 pm-8:56 pm

1 stop8h 18m

Ontario

Fri 9/12

8:59 pm-9:06 am

1 stop10h 07m

$143

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 9/25

10:49 am-3:29 pm

1 stop6h 40m

Ontario

Sat 9/27

8:59 pm-9:06 am

1 stop10h 07m

$144

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 11/1

7:00 am-3:17 pm

1 stop10h 17m

Ontario

Sun 11/9

6:53 am-9:07 am

1 stop24h 14m

$281

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 10/8

6:50 am-12:14 pm

1 stop7h 24m

Ontario

Wed 10/22

6:00 am-1:39 pm

1 stop5h 39m

$287

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 10/4

1:26 pm-7:15 pm

1 stop7h 49m

Ontario

Wed 10/22

9:50 am-6:40 pm

1 stop6h 50m

$297

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 9/16

5:18 am-10:03 am

1 stop6h 45m

Ontario

Tue 9/30

1:10 pm-10:50 pm

2 stops7h 40m

$298

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 9/16

8:50 am-4:05 pm

2 stops9h 15m

Ontario

Tue 9/30

1:10 pm-10:50 pm

2 stops7h 40m

$303

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 10/3

3:35 pm-12:03 am

1 stop10h 28m

Ontario

Tue 10/21

1:31 pm-12:03 am

1 stop8h 32m

$322

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 2/7

2:55 pm-10:37 pm

1 stop9h 42m

Ontario

Wed 2/11

6:55 pm-1:52 pm

1 stop16h 57m

$326

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 20 resultsSorted by cheapest first
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How to get the cheapest flight ticket from St. Louis to Ontario

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

What is the cheapest month to fly to Ontario?

In general, February is the cheapest month to fly from St. Louis to Ontario. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $256. If you aren’t able to travel during the month of February, then book flights to Ontario from St. Louis during August instead. Flights to Ontario in August, while not as cheap as those in February, still average around $302.

What is the cheapest day to depart on your flight to Ontario?

The cheapest day to depart on your flight to Ontario is on a Tuesday when prices can be found for as low as $291. This is often the case because there is less demand to fly during this day of the week. When flying out on a Sunday, the most expensive travel day of the week, you can expect to see flight prices from St. Louis to Ontario for around $376.

What is the cheapest time of day to depart on your flight to Ontario?

In the afternoon is the cheapest time of day to fly from St. Louis to Ontario when you can find flight prices for as low as $361. Flying to Ontario in the afternoon is an ideal time because this is during off-peak travel hours. If you have a flexible travel schedule, then try to avoid flying in the morning when prices are $442 on average. Flights to Ontario from St. Louis in the morning are generally more expensive because this time of day is more convenient for travelers’ schedules.

How far in advance should I book a flight to Ontario?

You are more likely to see cheaper flights to Ontario from St. Louis when booking weeks ahead of your departure date. In general, you can expect to find flights to Ontario for around $373 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Ontario from St. Louis for as low as $130 on momondo.

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

As of August 2025, prices for St. Louis to Ontario flights are approximately 43% more expensive when compared to flights at the same time last year.

When to book flights from St. Louis to Ontario

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

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

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

Direct flights

None
There are no direct flights from St. Louis to Ontario. There are no popular flight routes from St. Louis to Ontario.
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  • How far is Lambert-St Louis to Ontario by plane?

    A flight from Lambert-St Louis to Ontario will travel around 1552.8 mi. 5h 58m is a normal flight duration for this route.

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

    Prices for flights from Lambert-St Louis Airport to Ontario Airport are refreshed on a daily basis.

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

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

    The minimum age a child must be to fly alone is five but airlines that offer an unaccompanied minor (UNMR) service will have their own age restrictions, including rules around flight length, timings, and stopovers. We always recommend checking with the individual airline you are booking with to travel from Lambert-St Louis Airport to Ontario Airport.

  • What documentation or ID do you need to fly to Ontario Airport?

    The required travel and health documents for your Ontario Airport trip may vary depending on your itinerary and personal circumstances. As a general rule, you should carry multiple documents, including a national ID card or driver's license and a passport valid for six months after your intended arrival at Ontario Airport. We recommend that you seek guidance from your airline or a reliable third party such as IATA.

  • What is the most popular airline from St. Louis to Ontario?

Best airlines flying from St. Louis to Ontario

Compare and see reviews for airlines that fly from St. Louis to Ontario with momondo
Airline
Rating
Free Cancellation
Price
FrontierPriceFrom $128Free CancellationRating
5.8
3,204 reviews
Search Frontier flights
DeltaPriceFrom $181Free CancellationRating
7.9
7,977 reviews
Search Delta flights
American AirlinesPriceFrom $264Free CancellationRating
7.2
10,000 reviews
Search American Airlines flights
SouthwestPriceFrom $336Free CancellationRating
8.0
4,242 reviews
Search Southwest flights
United AirlinesPriceFrom $344Free CancellationRating
7.4
8,944 reviews
Search United Airlines flights

  • Southwest Flights From St. Louis to Ontario

    Southwest operates around 6 flights from St. Louis to Ontario every week. The average price of these flights found in the last 72 hours has been $407, but momondo users have found Southwest deals from St. Louis to Ontario from as low as $336 round-trip. Southwest has been scored 8.0/10 in 4,242 reviews.

Why use momondo?

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

Finding the right flight to Ontario from St. Louis is quick and easy when you have a range of options in front of you, from reputable agents and recognisable airlines. Options that can then be filtered down to find the best fit. That is what momondo does. We make finding flights to Ontario quick and easy, saving you time and money.

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

Yes. momondo enables you to select and highlight flights to Ontario from St. Louis with this policy.

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

momondo helps you find the best flight between St. Louis and Ontario by providing filters to narrow your choice of flights to those matching your criteria. You can select flights based on numerous factors such as price, departure and landing times, airport and airline.

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

If you are simply researching potential flights to Ontario, momondo offers a useful price alert feature which will track prices for flights to Ontario from St. Louis and alert you when they change.

An easier way to manage your Ontario trip

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