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Cheap flights from St. Louis to Los Angeles from $85

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 4/20. 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

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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
9:55 pm - 8:04 am
STL
-
ONT
12h 09m
1 stop
Frontier Logo
6:00 am - 7:23 pm
ONT
-
STL
11h 23m
1 stop
$160Frontier
Sun, May 3 - Thu, May 7
Frontier Logo
9:55 pm - 8:24 am
STL
-
ONT
12h 29m
1 stop
Frontier Logo
5:33 pm - 7:32 pm
ONT
-
STL
23h 59m
1 stop
$196Frontier
Thu, Apr 23 - Fri, Apr 24
Frontier Logo
9:55 pm - 10:44 am
STL
-
ONT
14h 49m
1 stop
Frontier Logo
9:59 pm - 3:21 pm
ONT
-
STL
15h 22m
1 stop
$198Frontier
Fri, Apr 17 - Fri, Apr 24
Frontier Logo
10:12 pm - 8:04 am
STL
-
ONT
11h 52m
1 stop
Frontier Logo
10:27 pm - 11:27 am
ONT
-
STL
11h 00m
1 stop
$200Frontier
Sun, Apr 5 - Thu, Apr 9
Frontier Logo
12:22 pm - 8:07 pm
STL
-
ONT
9h 45m
1 stop
Frontier Logo
5:33 pm - 7:32 pm
ONT
-
STL
23h 59m
1 stop
$205Frontier
Mon, Apr 13 - Fri, Apr 17
Frontier Logo
9:55 pm - 8:04 am
STL
-
ONT
12h 09m
1 stop
Frontier Logo
6:00 am - 7:23 pm
ONT
-
STL
11h 23m
1 stop
$210Frontier
Sun, May 3 - Thu, May 7
Frontier Logo
9:55 pm - 10:44 am
STL
-
ONT
14h 49m
1 stop
Frontier Logo
6:15 am - 2:36 pm
ONT
-
STL
6h 21m
1 stop
$212Frontier
Fri, Apr 17 - Mon, Apr 20
Frontier Logo
12:17 pm - 12:09 pm
STL
-
ONT
25h 52m
1 stop
Frontier Logo
6:20 am - 9:48 am
ONT
-
STL
25h 28m
1 stop
$216Frontier
Mon, Apr 6 - Fri, Apr 10
Frontier Logo
1:14 pm - 8:04 am
STL
-
ONT
20h 50m
1 stop
Frontier Logo
12:59 am - 7:21 pm
ONT
-
STL
16h 22m
1 stop
$217Frontier
Thu, Apr 9 - Wed, Apr 15
Frontier Logo
3:21 pm - 11:43 pm
STL
-
ONT
10h 22m
1 stop
Frontier Logo
7:44 pm - 9:00 pm
ONT
-
STL
23h 16m
1 stop
$221Frontier
Mon, Apr 27 - Wed, Apr 29

Southwest flights from St. Louis to Ontario

Our best Southwest deals on St. Louis to Ontario flight tickets
Southwest
Apr 14
STL6:35 amLambert-St Louis
5h 40m
1 stop
ONT10:15 amOntario
Apr 21
ONT12:55 pmOntario
7h 25m
1 stop
STL10:20 pmLambert-St Louis
$333
Southwest
Apr 14
STL8:25 amLambert-St Louis
9h 25m
2 stops
ONT3:50 pmOntario
Apr 21
ONT2:25 pmOntario
4h 45m
1 stop
STL9:10 pmLambert-St Louis
$338

American Airlines flights from St. Louis to Ontario

Our best American Airlines deals on St. Louis to Ontario flight tickets
American Airlines
Apr 14
STL12:27 pmLambert-St Louis
7h 57m
2 stops
ONT6:24 pmOntario
Apr 21
ONT6:15 amOntario
9h 06m
2 stops
STL5:21 pmLambert-St Louis
$343
American Airlines
Apr 5
STL9:35 amLambert-St Louis
8h 47m
2 stops
ONT4:22 pmOntario
Apr 9
ONT12:19 pmOntario
9h 27m
2 stops
STL11:46 pmLambert-St Louis
$518

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 March 22, 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

Sun 5/3

9:55 pm-8:04 am

1 stop12h 09m

Ontario

Thu 5/7

6:00 am-7:23 pm

1 stop11h 23m

$160

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 4/23

9:55 pm-8:24 am

1 stop12h 29m

Ontario

Fri 4/24

5:33 pm-7:32 pm

1 stop23h 59m

$196

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 4/17

9:55 pm-10:44 am

1 stop14h 49m

Ontario

Fri 4/24

9:59 pm-3:21 pm

1 stop15h 22m

$198

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sun 4/5

10:12 pm-8:04 am

1 stop11h 52m

Ontario

Thu 4/9

10:27 pm-11:27 am

1 stop11h 00m

$200

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 4/13

12:22 pm-8:07 pm

1 stop9h 45m

Ontario

Fri 4/17

5:33 pm-7:32 pm

1 stop23h 59m

$205

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sun 5/3

9:55 pm-8:04 am

1 stop12h 09m

Ontario

Thu 5/7

6:00 am-7:23 pm

1 stop11h 23m

$210
Quickest round-trip

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 4/17

9:55 pm-10:44 am

1 stop14h 49m

Ontario

Mon 4/20

6:15 am-2:36 pm

1 stop6h 21m

$212

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 4/6

12:17 pm-12:09 pm

1 stop25h 52m

Ontario

Fri 4/10

6:20 am-9:48 am

1 stop25h 28m

$216

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 4/9

1:14 pm-8:04 am

1 stop20h 50m

Ontario

Wed 4/15

12:59 am-7:21 pm

1 stop16h 22m

$217

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 4/27

3:21 pm-11:43 pm

1 stop10h 22m

Ontario

Wed 4/29

7:44 pm-9:00 pm

1 stop23h 16m

$221

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, 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 $302.

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 $360 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 $285 on momondo.

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

As of March 2026, prices for St. Louis to Ontario flights are approximately 68% 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

Fastest flight time

5h 41m

Direct flights

None
The fastest flight from St. Louis to Ontario takes 5h 41m
There are no direct flights from St. Louis to Ontario. There are no popular flight routes from St. Louis to Ontario.
Search flight deals

  • 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 41m 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
5.7
3,018 reviews
Search Frontier flights
American AirlinesPriceFrom $264Free CancellationRating
7.1
11,489 reviews
Search American Airlines flights
DeltaPriceFrom $276Free CancellationRating
7.9
8,314 reviews
Search Delta flights
SouthwestPriceFrom $292Free CancellationRating
8.0
4,324 reviews
Search Southwest flights
United AirlinesPriceFrom $292Free CancellationRating
7.4
9,455 reviews
Search United Airlines flights

  • Southwest Flights From St. Louis to Ontario

    Southwest operates around 1 flight from St. Louis to Ontario every week. The average price of these flights found in the last 72 hours has been $400, but momondo users have found Southwest deals from St. Louis to Ontario from as low as $292 round-trip. Southwest has been scored 8.0/10 in 4,324 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

We make it super easy to schedule, organize and travel with friends or family. Trips is free — and available to use no matter where you book.
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