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Cheap flights from St. Louis to Los Angeles from $122

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 8/5. Fares may change, and may not be available for all flights or travel dates. Click the price to refresh the search for this deal.
1 adult
1 adult, Economy, 0 bags

Discover deals from 900+ travel sites with momondo.

Find the cheapest flights from St. Louis to Los Angeles

Cheap round-trip flights

Enter your travel dates to find the best prices.
Frontier Logo
8:08 pm - 11:50 pm
STL
-
ONT
29h 42m
1 stop
Frontier Logo
3:40 pm - 5:50 pm
ONT
-
STL
24h 10m
1 stop
$224Frontier
Tue, Aug 11 - Tue, Aug 18
Frontier Logo
8:00 am - 3:54 pm
STL
-
ONT
9h 54m
1 stop
Frontier Logo
3:40 pm - 5:50 pm
ONT
-
STL
24h 10m
1 stop
$230Frontier
Tue, Aug 18 - Tue, Aug 25
Frontier Logo
6:45 pm - 2:03 pm
STL
-
ONT
21h 18m
2 stops
Frontier Logo
3:40 pm - 5:50 pm
ONT
-
STL
24h 10m
1 stop
$235Frontier
Tue, Aug 18 - Tue, Aug 25
Frontier Logo
8:10 pm - 11:55 pm
STL
-
ONT
5h 45m
1 stop
Frontier Logo
11:16 am - 1:17 am
ONT
-
STL
12h 01m
1 stop
$248Frontier
Wed, Oct 21 - Sat, Oct 24
Frontier Logo
5:19 pm - 4:10 pm
STL
-
ONT
24h 51m
1 stop
Frontier Logo
11:16 am - 1:17 am
ONT
-
STL
12h 01m
1 stop
$251Frontier
Thu, Oct 15 - Tue, Oct 20
Frontier Logo
7:10 pm - 8:03 am
STL
-
ONT
14h 53m
1 stop
Frontier Logo
10:49 am - 7:23 pm
ONT
-
STL
6h 34m
1 stop
$254Frontier
Sat, Aug 1 - Sat, Aug 8
Frontier Logo
8:08 pm - 11:50 pm
STL
-
ONT
5h 42m
1 stop
Frontier Logo
10:49 am - 7:23 pm
ONT
-
STL
6h 34m
1 stop
$256Frontier
Wed, Jul 22 - Tue, Jul 28
Frontier Logo
6:45 pm - 4:22 pm
STL
-
ONT
23h 37m
1 stop
Frontier Logo
7:56 pm - 7:13 pm
ONT
-
STL
21h 17m
1 stop
$258Frontier
Wed, Aug 19 - Wed, Aug 26
Frontier Logo
12:46 pm - 8:54 pm
STL
-
ONT
10h 08m
1 stop
Frontier Logo
11:16 am - 1:17 am
ONT
-
STL
12h 01m
1 stop
$260Frontier
Wed, Oct 7 - Sat, Oct 10
Frontier Logo
7:03 pm - 8:03 am
STL
-
ONT
15h 00m
1 stop
Frontier Logo
10:49 am - 7:23 pm
ONT
-
STL
6h 34m
1 stop
$264Frontier
Tue, Jul 21 - Tue, Jul 28

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Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Aug 11
STL8:08 pmLambert-St Louis
29h 42m
1 stop
ONT11:50 pmOntario
Aug 18
ONT3:40 pmOntario
24h 10m
1 stop
STL5:50 pmLambert-St Louis
$224
Frontier
Aug 18
STL8:00 amLambert-St Louis
9h 54m
1 stop
ONT3:54 pmOntario
Aug 25
ONT3:40 pmOntario
24h 10m
1 stop
STL5:50 pmLambert-St Louis
$230
Frontier
Aug 18
STL6:45 pmLambert-St Louis
21h 18m
2 stops
ONT2:03 pmOntario
Aug 25
ONT3:40 pmOntario
24h 10m
1 stop
STL5:50 pmLambert-St Louis
$235

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 July 3, 2026.
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

Cheapest round-trip

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 8/11

8:08 pm-11:50 pm

1 stop29h 42m

Ontario

Tue 8/18

3:40 pm-5:50 pm

1 stop24h 10m

$224

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 8/18

8:00 am-3:54 pm

1 stop9h 54m

Ontario

Tue 8/25

3:40 pm-5:50 pm

1 stop24h 10m

$230

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 8/18

6:45 pm-2:03 pm

2 stops21h 18m

Ontario

Tue 8/25

3:40 pm-5:50 pm

1 stop24h 10m

$235

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 10/21

8:10 pm-11:55 pm

1 stop5h 45m

Ontario

Sat 10/24

11:16 am-1:17 am

1 stop12h 01m

$248

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 10/15

5:19 pm-4:10 pm

1 stop24h 51m

Ontario

Tue 10/20

11:16 am-1:17 am

1 stop12h 01m

$251

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 8/1

7:10 pm-8:03 am

1 stop14h 53m

Ontario

Sat 8/8

10:49 am-7:23 pm

1 stop6h 34m

$254
Quickest round-trip

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 7/22

8:08 pm-11:50 pm

1 stop5h 42m

Ontario

Tue 7/28

10:49 am-7:23 pm

1 stop6h 34m

$256

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 8/19

6:45 pm-4:22 pm

1 stop23h 37m

Ontario

Wed 8/26

7:56 pm-7:13 pm

1 stop21h 17m

$258

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 10/7

12:46 pm-8:54 pm

1 stop10h 08m

Ontario

Sat 10/10

11:16 am-1:17 am

1 stop12h 01m

$260

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 7/21

7:03 pm-8:03 am

1 stop15h 00m

Ontario

Tue 7/28

10:49 am-7:23 pm

1 stop6h 34m

$264

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

What is the cheapest month to fly to Ontario?

In general, November 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 $292. If you aren’t able to travel during the month of November, then book flights to Ontario from St. Louis during August instead. Flights to Ontario in August, while not as cheap as those in November, still average around $300.

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

As of July 2026, prices for St. Louis to Ontario flights are approximately 17% cheaper 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

Fastest flight time

5h 45m

Direct flights

None
The fastest flight from St. Louis to Ontario takes 5h 45m
There are no direct flights from St. Louis to Ontario. There are no popular flight routes from St. Louis to Ontario.
Search flight deals

Frequently asked questions about flying from St. Louis to Ontario

  • 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 45m 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 $143Free CancellationRating
5.6
2,847 reviews
Search Frontier flights
United AirlinesPriceFrom $201Free CancellationRating
7.4
9,927 reviews
Search United Airlines flights
American AirlinesPriceFrom $264Free CancellationRating
7.1
11,763 reviews
Search American Airlines flights
SouthwestPriceFrom $292Free CancellationRating
7.9
4,250 reviews
Search Southwest flights

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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