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Cheap flights from St. Louis to Los Angeles from $63

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 1/9. 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
1:16 pm - 1:10 pmSTL-ONT
25h 54m1 stop
Frontier Logo
6:15 am - 12:12 pmONT-STL
27h 57m1 stop
$130Frontier
Find Deal
Thu, Dec 4 - Thu, Dec 11
Frontier Logo
9:54 pm - 2:26 pmSTL-ONT
18h 32m1 stop
Frontier Logo
5:06 pm - 9:09 pmONT-STL
26h 03m1 stop
$137Frontier
Find Deal
Thu, Nov 20 - Sun, Nov 23
Frontier Logo
10:44 pm - 9:17 pmSTL-ONT
24h 33m1 stop
Frontier Logo
6:15 am - 9:48 pmONT-STL
13h 33m1 stop
$138Frontier
Find Deal
Fri, Dec 5 - Fri, Dec 12
Frontier Logo
9:54 pm - 9:17 pmSTL-ONT
25h 23m1 stop
Frontier Logo
3:20 pm - 10:14 amONT-STL
16h 54m1 stop
$141Frontier
Find Deal
Mon, Dec 1 - Fri, Dec 5
Frontier Logo
7:43 pm - 11:09 amSTL-ONT
17h 26m1 stop
Frontier Logo
4:01 pm - 10:14 amONT-STL
16h 13m1 stop
$142Frontier
Find Deal
Wed, Dec 10 - Sun, Dec 14
Frontier Logo
7:43 pm - 11:57 pmSTL-ONT
6h 14m1 stop
Frontier Logo
7:06 pm - 6:58 pmONT-STL
21h 52m1 stop
$144Frontier
Find Deal
Sat, Nov 22 - Mon, Nov 24
Frontier Logo
9:54 pm - 9:17 pmSTL-ONT
25h 23m1 stop
Frontier Logo
5:18 pm - 12:12 pmONT-STL
16h 54m1 stop
$145Frontier
Find Deal
Mon, Dec 1 - Sun, Dec 7
Multiple Airlines Logo
7:04 pm - 7:20 amSTL-ONT
14h 16m1 stop
Multiple Airlines Logo
3:21 pm - 10:33 pmONT-STL
29h 12m2 stops
$247Multiple Airlines
Find Deal
Mon, Nov 24 - Mon, Dec 1
Delta Logo
6:00 am - 5:07 pmSTL-ONT
13h 07m2 stops
Delta Logo
12:40 pm - 12:50 amONT-STL
10h 10m2 stops
$276Delta
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Tue, Dec 9 - Sat, Dec 13
Delta Logo
6:34 am - 12:18 pmSTL-ONT
7h 44m1 stop
Delta Logo
6:00 am - 3:05 pmONT-STL
7h 05m1 stop
$287Delta
Find Deal
Mon, Nov 24 - Thu, Nov 27

Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Dec 4
STL1:16 pmLambert-St Louis
25h 54m
1 stop
ONT1:10 pmOntario
Dec 11
ONT6:15 amOntario
27h 57m
1 stop
STL12:12 pmLambert-St Louis
$130
Find similar
Frontier
Nov 20
STL9:54 pmLambert-St Louis
18h 32m
1 stop
ONT2:26 pmOntario
Nov 23
ONT5:06 pmOntario
26h 03m
1 stop
STL9:09 pmLambert-St Louis
$137
Find similar
Frontier
Dec 5
STL10:44 pmLambert-St Louis
24h 33m
1 stop
ONT9:17 pmOntario
Dec 12
ONT6:15 amOntario
13h 33m
1 stop
STL9:48 pmLambert-St Louis
$138
Find similar

Delta flights from St. Louis to Ontario

Our best Delta deals on St. Louis to Ontario flight tickets
Delta
Dec 9
STL6:00 amLambert-St Louis
13h 07m
2 stops
ONT5:07 pmOntario
Dec 13
ONT12:40 pmOntario
10h 10m
2 stops
STL12:50 amLambert-St Louis
$276
Find similar
Delta
Nov 24
STL6:34 amLambert-St Louis
7h 44m
1 stop
ONT12:18 pmOntario
Nov 27
ONT6:00 amOntario
7h 05m
1 stop
STL3:05 pmLambert-St Louis
$287
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 November 9, 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

Thu 12/4

1:16 pm-1:10 pm

1 stop25h 54m

Ontario

Thu 12/11

6:15 am-12:12 pm

1 stop27h 57m

$130

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 11/20

9:54 pm-2:26 pm

1 stop18h 32m

Ontario

Sun 11/23

5:06 pm-9:09 pm

1 stop26h 03m

$137

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 12/5

10:44 pm-9:17 pm

1 stop24h 33m

Ontario

Fri 12/12

6:15 am-9:48 pm

1 stop13h 33m

$138

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 12/1

9:54 pm-9:17 pm

1 stop25h 23m

Ontario

Fri 12/5

3:20 pm-10:14 am

1 stop16h 54m

$141

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 12/10

7:43 pm-11:09 am

1 stop17h 26m

Ontario

Sun 12/14

4:01 pm-10:14 am

1 stop16h 13m

$142

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 11/22

7:43 pm-11:57 pm

1 stop6h 14m

Ontario

Mon 11/24

7:06 pm-6:58 pm

1 stop21h 52m

$144

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 12/1

9:54 pm-9:17 pm

1 stop25h 23m

Ontario

Sun 12/7

5:18 pm-12:12 pm

1 stop16h 54m

$145

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 11/24

7:04 pm-7:20 am

1 stop14h 16m

Ontario

Mon 12/1

3:21 pm-10:33 pm

2 stops29h 12m

$247

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 12/9

6:00 am-5:07 pm

2 stops13h 07m

Ontario

Sat 12/13

12:40 pm-12:50 am

2 stops10h 10m

$276

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 11/24

6:34 am-12:18 pm

1 stop7h 44m

Ontario

Thu 11/27

6:00 am-3:05 pm

1 stop7h 05m

$287

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 $170. 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 $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 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 $359 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 November 2025, prices for St. Louis to Ontario flights are approximately 29% 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

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. 6h 00m 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 $108Free CancellationRating
5.8
3,111 reviews
Search Frontier flights
DeltaPriceFrom $171Free CancellationRating
7.9
8,002 reviews
Search Delta flights
American AirlinesPriceFrom $264Free CancellationRating
7.2
11,050 reviews
Search American Airlines flights
SouthwestPriceFrom $292Free CancellationRating
8.0
4,240 reviews
Search Southwest flights
United AirlinesPriceFrom $292Free CancellationRating
7.4
9,012 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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