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Cheap flights from St. Louis to Los Angeles from $72

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 9/25. 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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Cheap round-trip flights

Frontier Logo
7:55 pm - 7:54 pmSTL-ONT
25h 59m1 stop
Frontier Logo
7:04 am - 9:07 amONT-STL
24h 03m1 stop
$142Frontier
Find Deal
vie., oct. 3 - mar., oct. 7
Frontier Logo
7:52 pm - 11:50 pmSTL-ONT
5h 58m1 stop
Frontier Logo
8:00 am - 3:56 pmONT-STL
5h 56m1 stop
$143Frontier
Find Deal
sáb., oct. 11 - sáb., oct. 18
Frontier Logo
7:52 pm - 11:50 pmSTL-ONT
5h 58m1 stop
Frontier Logo
10:47 pm - 11:43 amONT-STL
10h 56m1 stop
$144Frontier
Find Deal
jue., oct. 23 - dom., oct. 26
Frontier Logo
2:38 pm - 7:17 amSTL-ONT
18h 39m1 stop
Frontier Logo
6:53 am - 9:07 amONT-STL
24h 14m1 stop
$145Frontier
Find Deal
dom., oct. 5 - dom., oct. 12
Frontier Logo
7:52 pm - 11:50 pmSTL-ONT
5h 58m1 stop
Frontier Logo
8:00 am - 3:56 pmONT-STL
5h 56m1 stop
$155Frontier
Find Deal
vie., oct. 24 - sáb., oct. 25
Frontier Logo
10:17 am - 3:32 pmSTL-ONT
7h 15m1 stop
Frontier Logo
10:47 pm - 11:43 amONT-STL
10h 56m1 stop
$156Frontier
Find Deal
jue., oct. 16 - dom., oct. 19
Frontier Logo
7:45 pm - 11:50 pmSTL-ONT
6h 05m1 stop
Frontier Logo
8:45 am - 9:07 amONT-STL
22h 22m1 stop
$157Frontier
Find Deal
jue., nov. 6 - mié., nov. 12
Frontier Logo
7:52 pm - 11:50 pmSTL-ONT
5h 58m1 stop
Frontier Logo
6:05 am - 11:43 amONT-STL
27h 38m1 stop
$158Frontier
Find Deal
jue., oct. 9 - jue., oct. 16
Frontier Logo
10:17 am - 3:32 pmSTL-ONT
7h 15m1 stop
Frontier Logo
6:53 am - 9:07 amONT-STL
24h 14m1 stop
$170Frontier
Find Deal
jue., oct. 16 - lun., oct. 20
Multiple Airlines Logo
7:52 pm - 11:50 pmSTL-ONT
5h 58m1 stop
Multiple Airlines Logo
1:31 pm - 12:03 amONT-STL
8h 32m1 stop
$268Multiple Airlines
Find Deal
sáb., oct. 11 - sáb., oct. 18

Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Oct 3
STL7:55 pmLambert-St Louis
25h 59m
1 stop
ONT7:54 pmOntario
Oct 7
ONT7:04 amOntario
24h 03m
1 stop
STL9:07 amLambert-St Louis
$142
Find similar
Frontier
Oct 11
STL7:52 pmLambert-St Louis
5h 58m
1 stop
ONT11:50 pmOntario
Oct 18
ONT8:00 amOntario
5h 56m
1 stop
STL3:56 pmLambert-St Louis
$143
Find similar
Frontier
Sep 25
STL10:49 amLambert-St Louis
6h 40m
1 stop
ONT3:29 pmOntario
Sep 30
ONT8:59 pmOntario
10h 07m
1 stop
STL9:06 amLambert-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
Sep 24
STL9:57 amLambert-St Louis
13h 27m
1 stop
ONT9:24 pmOntario
Sep 28
ONT10:35 pmOntario
12h 37m
1 stop
STL1:12 pmLambert-St Louis
$638
Find similar
American Airlines
Sep 24
STL8:00 amLambert-St Louis
10h 05m
1 stop
ONT4:05 pmOntario
Sep 28
ONT1:10 pmOntario
8h 38m
2 stops
STL11:48 pmLambert-St Louis
$699
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 septiembre 17, 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

vie. 10/3

7:55 pm-7:54 pm

1 stop25h 59m

Ontario

mar. 10/7

7:04 am-9:07 am

1 stop24h 03m

$142

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

sáb. 10/11

7:52 pm-11:50 pm

1 stop5h 58m

Ontario

sáb. 10/18

8:00 am-3:56 pm

1 stop5h 56m

$143

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

jue. 10/23

7:52 pm-11:50 pm

1 stop5h 58m

Ontario

dom. 10/26

10:47 pm-11:43 am

1 stop10h 56m

$144

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

dom. 10/5

2:38 pm-7:17 am

1 stop18h 39m

Ontario

dom. 10/12

6:53 am-9:07 am

1 stop24h 14m

$145

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

vie. 10/24

7:52 pm-11:50 pm

1 stop5h 58m

Ontario

sáb. 10/25

8:00 am-3:56 pm

1 stop5h 56m

$155

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

jue. 10/16

10:17 am-3:32 pm

1 stop7h 15m

Ontario

dom. 10/19

10:47 pm-11:43 am

1 stop10h 56m

$156

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

jue. 11/6

7:45 pm-11:50 pm

1 stop6h 05m

Ontario

mié. 11/12

8:45 am-9:07 am

1 stop22h 22m

$157

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

jue. 10/9

7:52 pm-11:50 pm

1 stop5h 58m

Ontario

jue. 10/16

6:05 am-11:43 am

1 stop27h 38m

$158

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

jue. 10/16

10:17 am-3:32 pm

1 stop7h 15m

Ontario

lun. 10/20

6:53 am-9:07 am

1 stop24h 14m

$170

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

sáb. 10/11

7:52 pm-11:50 pm

1 stop5h 58m

Ontario

sáb. 10/18

1:31 pm-12:03 am

1 stop8h 32m

$268

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 $256. 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 $374 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 September 2025, prices for St. Louis to Ontario flights are approximately 25% 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

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. 5h 51m 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
5.8
3,173 reviews
Search Frontier flights
DeltaPriceFrom $181Free CancellationRating
7.9
7,961 reviews
Search Delta flights
American AirlinesPriceFrom $264Free CancellationRating
7.2
10,000 reviews
Search American Airlines flights
United AirlinesPriceFrom $332Free CancellationRating
7.4
8,926 reviews
Search United Airlines flights
SouthwestPriceFrom $336Free CancellationRating
8.0
4,242 reviews
Search Southwest 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 $416, but momondo users have found Southwest deals from St. Louis to Ontario from as low as $336 round-trip. Southwest has been scored 8.0/10 in 4,242 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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