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Cheap flights from St. Louis to Los Angeles from $87

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 4/24. 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
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 - 6:49 pm
STL
-
ONT
22h 54m
1 stop
Frontier Logo
12:59 am - 7:21 pm
ONT
-
STL
16h 22m
1 stop
$190Frontier
Fri, Apr 17 - Sat, Apr 18
Frontier Logo
9:55 pm - 10:44 am
STL
-
ONT
14h 49m
1 stop
Frontier Logo
5:33 pm - 7:32 pm
ONT
-
STL
23h 59m
1 stop
$201Frontier
Mon, Apr 20 - Fri, Apr 24
Frontier Logo
8:16 pm - 11:56 pm
STL
-
ONT
5h 40m
1 stop
Frontier Logo
12:59 am - 7:21 pm
ONT
-
STL
16h 22m
1 stop
$211Frontier
Fri, Apr 10 - Thu, Apr 23
Frontier Logo
8:16 pm - 11:56 pm
STL
-
ONT
5h 40m
1 stop
Frontier Logo
12:59 am - 7:32 pm
ONT
-
STL
16h 33m
1 stop
$212Frontier
Fri, Apr 10 - Fri, Apr 17
Frontier Logo
9:55 pm - 9:04 pm
STL
-
ONT
25h 09m
1 stop
Frontier Logo
12:59 am - 7:21 pm
ONT
-
STL
16h 22m
1 stop
$213Frontier
Thu, Apr 23 - Sat, Apr 25
Frontier Logo
8:16 pm - 11:56 pm
STL
-
ONT
5h 40m
1 stop
Frontier Logo
10:35 pm - 11:22 am
ONT
-
STL
10h 47m
1 stop
$220Frontier
Wed, Apr 1 - Sun, Apr 5
Frontier Logo
8:06 pm - 7:31 am
STL
-
ONT
13h 25m
1 stop
Frontier Logo
12:59 am - 7:32 pm
ONT
-
STL
16h 33m
1 stop
$222Frontier
Thu, Apr 30 - Sun, May 3
Frontier Logo
9:55 pm - 8:24 am
STL
-
ONT
12h 29m
1 stop
Frontier Logo
12:59 am - 7:32 pm
ONT
-
STL
16h 33m
1 stop
$224Frontier
Thu, Apr 16 - Fri, Apr 17
Frontier Logo
10:12 pm - 8:04 am
STL
-
ONT
11h 52m
1 stop
Frontier Logo
6:20 am - 9:48 am
ONT
-
STL
25h 28m
1 stop
$225Frontier
Thu, Apr 2 - Fri, Apr 10
Frontier Logo
9:55 pm - 8:04 pm
STL
-
ONT
24h 09m
1 stop
Frontier Logo
12:59 am - 7:32 pm
ONT
-
STL
16h 33m
1 stop
$232Frontier
Thu, Apr 16 - Sun, Apr 19

Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Apr 17
STL9:55 pmLambert-St Louis
22h 54m
1 stop
ONT6:49 pmOntario
Apr 18
ONT12:59 amOntario
16h 22m
1 stop
STL7:21 pmLambert-St Louis
$190
Frontier
Apr 20
STL9:55 pmLambert-St Louis
14h 49m
1 stop
ONT10:44 amOntario
Apr 24
ONT5:33 pmOntario
23h 59m
1 stop
STL7:32 pmLambert-St Louis
$201
Frontier
Apr 10
STL8:16 pmLambert-St Louis
5h 40m
1 stop
ONT11:56 pmOntario
Apr 23
ONT12:59 amOntario
16h 22m
1 stop
STL7:21 pmLambert-St Louis
$211

United Airlines flights from St. Louis to Ontario

Our best United Airlines deals on St. Louis to Ontario flight tickets
United Airlines
May 5
STL8:46 amLambert-St Louis
5h 52m
1 stop
ONT12:38 pmOntario
May 6
ONT6:00 amOntario
12h 43m
2 stops
STL8:43 pmLambert-St Louis
$282
United Airlines
May 14
STL2:35 pmLambert-St Louis
8h 01m
1 stop
ONT8:36 pmOntario
May 19
ONT6:00 amOntario
12h 43m
2 stops
STL8:43 pmLambert-St Louis
$323

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 February 27, 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

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 4/17

9:55 pm-6:49 pm

1 stop22h 54m

Ontario

Sat 4/18

12:59 am-7:21 pm

1 stop16h 22m

$190

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 4/20

9:55 pm-10:44 am

1 stop14h 49m

Ontario

Fri 4/24

5:33 pm-7:32 pm

1 stop23h 59m

$201

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 4/10

8:16 pm-11:56 pm

1 stop5h 40m

Ontario

Thu 4/23

12:59 am-7:21 pm

1 stop16h 22m

$211

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 4/10

8:16 pm-11:56 pm

1 stop5h 40m

Ontario

Fri 4/17

12:59 am-7:32 pm

1 stop16h 33m

$212

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 4/23

9:55 pm-9:04 pm

1 stop25h 09m

Ontario

Sat 4/25

12:59 am-7:21 pm

1 stop16h 22m

$213

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 4/1

8:16 pm-11:56 pm

1 stop5h 40m

Ontario

Sun 4/5

10:35 pm-11:22 am

1 stop10h 47m

$220

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 4/30

8:06 pm-7:31 am

1 stop13h 25m

Ontario

Sun 5/3

12:59 am-7:32 pm

1 stop16h 33m

$222

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 4/16

9:55 pm-8:24 am

1 stop12h 29m

Ontario

Fri 4/17

12:59 am-7:32 pm

1 stop16h 33m

$224

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 4/2

10:12 pm-8:04 am

1 stop11h 52m

Ontario

Fri 4/10

6:20 am-9:48 am

1 stop25h 28m

$225

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 4/16

9:55 pm-8:04 pm

1 stop24h 09m

Ontario

Sun 4/19

12:59 am-7:32 pm

1 stop16h 33m

$232

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.

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 $344 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 $163 on momondo.

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

As of February 2026, prices for St. Louis to Ontario flights are approximately 63% 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 40m

Direct flights

None
The fastest flight from St. Louis to Ontario takes 5h 40m
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 40m 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
3,041 reviews
Search Frontier flights
DeltaPriceFrom $190Free CancellationRating
7.9
8,242 reviews
Search Delta flights
American AirlinesPriceFrom $265Free CancellationRating
7.2
11,357 reviews
Search American Airlines flights
SouthwestPriceFrom $292Free CancellationRating
8.0
4,301 reviews
Search Southwest flights
United AirlinesPriceFrom $292Free CancellationRating
7.4
9,349 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 $386, 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 4,301 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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