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Cheap flights from St. Louis to Los Angeles from $81

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 2/21. 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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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
3:43 pm - 10:59 pm
STL
-
ONT
9h 16m1 stop
Frontier Logo
7:15 am - 2:46 pm
ONT
-
STL
29h 31m1 stop
$133Frontier
Sat, Jan 17 - Tue, Jan 20
Frontier Logo
9:46 pm - 7:36 am
STL
-
ONT
11h 50m1 stop
Frontier Logo
7:15 am - 2:46 pm
ONT
-
STL
29h 31m1 stop
$142Frontier
Sun, Jan 11 - Tue, Jan 20
Frontier Logo
3:43 pm - 10:59 pm
STL
-
ONT
9h 16m1 stop
Frontier Logo
8:48 pm - 8:48 pm
ONT
-
STL
22h 00m1 stop
$144Frontier
Sat, Jan 17 - Thu, Jan 22
Frontier Logo
3:46 pm - 11:24 pm
STL
-
ONT
9h 38m1 stop
Frontier Logo
7:15 am - 2:46 pm
ONT
-
STL
5h 31m1 stop
$148Frontier
Sat, Jan 24 - Wed, Jan 28
Frontier Logo
3:46 pm - 11:24 pm
STL
-
ONT
9h 38m1 stop
Frontier Logo
7:15 am - 11:18 am
ONT
-
STL
26h 03m1 stop
$149Frontier
Sat, Jan 24 - Sat, Jan 31
Frontier Logo
9:46 pm - 7:36 am
STL
-
ONT
11h 50m1 stop
Frontier Logo
8:48 pm - 8:48 pm
ONT
-
STL
22h 00m1 stop
$156Frontier
Sun, Jan 11 - Thu, Jan 22
Frontier Logo
3:43 pm - 10:59 pm
STL
-
ONT
9h 16m1 stop
Frontier Logo
10:18 am - 8:48 pm
ONT
-
STL
8h 30m1 stop
$158Frontier
Sat, Jan 17 - Fri, Jan 23
Frontier Logo
3:46 pm - 11:24 pm
STL
-
ONT
9h 38m1 stop
Frontier Logo
11:04 am - 9:06 pm
ONT
-
STL
8h 02m1 stop
$165Frontier
Sat, Jan 24 - Thu, Jan 29
Frontier Logo
3:28 pm - 9:34 pm
STL
-
ONT
8h 06m1 stop
Frontier Logo
7:30 am - 3:53 pm
ONT
-
STL
6h 23m1 stop
$166Frontier
Wed, Feb 11 - Wed, Feb 18
Frontier Logo
3:43 pm - 10:59 pm
STL
-
ONT
9h 16m1 stop
Frontier Logo
3:07 pm - 2:46 pm
ONT
-
STL
21h 39m2 stops
$169Frontier
Sat, Jan 17 - Tue, Jan 20

Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Jan 17
STL3:43 pmLambert-St Louis
9h 16m
1 stop
ONT10:59 pmOntario
Jan 20
ONT7:15 amOntario
29h 31m
1 stop
STL2:46 pmLambert-St Louis
$133
Find similar
Frontier
Jan 11
STL9:46 pmLambert-St Louis
11h 50m
1 stop
ONT7:36 amOntario
Jan 20
ONT7:15 amOntario
29h 31m
1 stop
STL2:46 pmLambert-St Louis
$142
Find similar
Frontier
Jan 17
STL3:43 pmLambert-St Louis
9h 16m
1 stop
ONT10:59 pmOntario
Jan 22
ONT8:48 pmOntario
22h 00m
1 stop
STL8:48 pmLambert-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
Jan 1
STL7:00 amLambert-St Louis
6h 53m
1 stop
ONT11:53 amOntario
Jan 1
ONT4:47 pmOntario
5h 04m
1 stop
STL11:51 pmLambert-St Louis
$381
Find similar
American Airlines
Jan 6
STL9:25 amLambert-St Louis
10h 55m
2 stops
ONT6:20 pmOntario
Jan 9
ONT6:00 amOntario
8h 14m
1 stop
STL4:14 pmLambert-St Louis
$562
Find similar
American Airlines
Jan 6
STL9:25 amLambert-St Louis
10h 55m
2 stops
ONT6:20 pmOntario
Jan 9
ONT9:59 amOntario
9h 16m
2 stops
STL9:15 pmLambert-St Louis
$567
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 December 23, 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

Sat 1/17

3:43 pm-10:59 pm

1 stop9h 16m

Ontario

Tue 1/20

7:15 am-2:46 pm

1 stop29h 31m

$133

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sun 1/11

9:46 pm-7:36 am

1 stop11h 50m

Ontario

Tue 1/20

7:15 am-2:46 pm

1 stop29h 31m

$142

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 1/17

3:43 pm-10:59 pm

1 stop9h 16m

Ontario

Thu 1/22

8:48 pm-8:48 pm

1 stop22h 00m

$144

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 1/24

3:46 pm-11:24 pm

1 stop9h 38m

Ontario

Wed 1/28

7:15 am-2:46 pm

1 stop5h 31m

$148

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 1/24

3:46 pm-11:24 pm

1 stop9h 38m

Ontario

Sat 1/31

7:15 am-11:18 am

1 stop26h 03m

$149

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sun 1/11

9:46 pm-7:36 am

1 stop11h 50m

Ontario

Thu 1/22

8:48 pm-8:48 pm

1 stop22h 00m

$156

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 1/17

3:43 pm-10:59 pm

1 stop9h 16m

Ontario

Fri 1/23

10:18 am-8:48 pm

1 stop8h 30m

$158

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 1/24

3:46 pm-11:24 pm

1 stop9h 38m

Ontario

Thu 1/29

11:04 am-9:06 pm

1 stop8h 02m

$165

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 2/11

3:28 pm-9:34 pm

1 stop8h 06m

Ontario

Wed 2/18

7:30 am-3:53 pm

1 stop6h 23m

$166

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 1/17

3:43 pm-10:59 pm

1 stop9h 16m

Ontario

Tue 1/20

3:07 pm-2:46 pm

2 stops21h 39m

$169

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 $301.

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

As of December 2025, prices for St. Louis to Ontario flights are approximately 85% 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 58m

Direct flights

None
The fastest flight from St. Louis to Ontario takes 5h 58m
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 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 $143Free CancellationRating
5.8
3,075 reviews
Search Frontier flights
DeltaPriceFrom $171Free CancellationRating
7.9
8,014 reviews
Search Delta flights
American AirlinesPriceFrom $264Free CancellationRating
7.2
11,054 reviews
Search American Airlines flights
SouthwestPriceFrom $292Free CancellationRating
8.0
4,253 reviews
Search Southwest flights
United AirlinesPriceFrom $292Free CancellationRating
7.4
9,105 reviews
Search United Airlines 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

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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