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Cheap flights from St. Louis to Los Angeles from $74

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 2/18. 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

Enter your travel dates to find the best prices.
Frontier Logo
7:39 pm - 12:20 am
STL
-
ONT
6h 41m1 stop
Frontier Logo
5:21 pm - 8:50 pm
ONT
-
STL
25h 29m1 stop
$149Frontier
vie., ene. 30 - dom., feb. 1
Frontier Logo
7:43 pm - 11:59 pm
STL
-
ONT
6h 16m1 stop
Frontier Logo
7:00 am - 10:02 am
ONT
-
STL
25h 02m1 stop
$160Frontier
sáb., feb. 21 - mar., feb. 24
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
$165Frontier
sáb., ene. 24 - sáb., ene. 31
Frontier Logo
7:43 pm - 11:56 pm
STL
-
ONT
6h 13m1 stop
Frontier Logo
10:18 pm - 12:40 pm
ONT
-
STL
12h 22m1 stop
$182Frontier
lun., ene. 12 - jue., ene. 15
Frontier Logo
10:10 pm - 3:09 pm
STL
-
ONT
18h 59m1 stop
Frontier Logo
3:21 pm - 11:39 am
ONT
-
STL
18h 18m1 stop
$183Frontier
lun., ene. 5 - sáb., ene. 10
Frontier Logo
10:01 pm - 1:32 pm
STL
-
ONT
17h 31m1 stop
Frontier Logo
5:21 pm - 8:50 pm
ONT
-
STL
25h 29m1 stop
$187Frontier
jue., ene. 29 - dom., feb. 1
Frontier Logo
1:35 pm - 5:44 pm
STL
-
ONT
6h 09m1 stop
Frontier Logo
1:05 pm - 8:50 pm
ONT
-
STL
5h 45m1 stop
$201Frontier
lun., ene. 19 - lun., ene. 26
Frontier Logo
3:43 pm - 9:23 pm
STL
-
ONT
31h 40m2 stops
Frontier Logo
10:18 pm - 12:40 pm
ONT
-
STL
12h 22m1 stop
$202Frontier
jue., ene. 8 - jue., ene. 15
Frontier Logo
7:43 pm - 11:56 pm
STL
-
ONT
6h 13m1 stop
Frontier Logo
10:18 pm - 12:40 pm
ONT
-
STL
12h 22m1 stop
$203Frontier
lun., ene. 12 - jue., ene. 15
Frontier Logo
10:10 pm - 9:17 pm
STL
-
ONT
25h 07m1 stop
Frontier Logo
6:00 am - 9:25 pm
ONT
-
STL
13h 25m1 stop
$209Frontier
dom., dic. 21 - sáb., dic. 27

Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Jan 30
STL7:39 pmLambert-St Louis
6h 41m
1 stop
ONT12:20 amOntario
Feb 1
ONT5:21 pmOntario
25h 29m
1 stop
STL8:50 pmLambert-St Louis
$149
Find similar
Frontier
Feb 21
STL7:43 pmLambert-St Louis
6h 16m
1 stop
ONT11:59 pmOntario
Feb 24
ONT7:00 amOntario
25h 02m
1 stop
STL10:02 amLambert-St Louis
$160
Find similar
Frontier
Jan 24
STL3:46 pmLambert-St Louis
9h 38m
1 stop
ONT11:24 pmOntario
Jan 31
ONT7:15 amOntario
5h 31m
1 stop
STL2:46 pmLambert-St Louis
$165
Find similar

Alaska Airlines flights from St. Louis to Ontario

Our best Alaska Airlines deals on St. Louis to Ontario flight tickets
Alaska Airlines
Jan 5
STL5:26 pmLambert-St Louis
8h 48m
1 stop
ONT12:14 amOntario
Jan 12
ONT11:53 amOntario
24h 01m
1 stop
STL1:54 pmLambert-St Louis
$318
Find similar
Alaska Airlines
Jan 20
STL2:50 pmLambert-St Louis
26h 18m
1 stop
ONT3:08 pmOntario
Jan 27
ONT11:53 amOntario
24h 01m
1 stop
STL1:54 pmLambert-St Louis
$344
Find similar
Alaska Airlines
Jan 13
STL2:50 pmLambert-St Louis
24h 16m
2 stops
ONT1:06 pmOntario
Jan 20
ONT7:56 pmOntario
15h 58m
2 stops
STL1:54 pmLambert-St Louis
$355
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 diciembre 11, 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. 1/30

7:39 pm-12:20 am

1 stop6h 41m

Ontario

dom. 2/1

5:21 pm-8:50 pm

1 stop25h 29m

$149

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

sáb. 2/21

7:43 pm-11:59 pm

1 stop6h 16m

Ontario

mar. 2/24

7:00 am-10:02 am

1 stop25h 02m

$160

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

sáb. 1/24

3:46 pm-11:24 pm

1 stop9h 38m

Ontario

sáb. 1/31

7:15 am-2:46 pm

1 stop5h 31m

$165

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

lun. 1/12

7:43 pm-11:56 pm

1 stop6h 13m

Ontario

jue. 1/15

10:18 pm-12:40 pm

1 stop12h 22m

$182

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

lun. 1/5

10:10 pm-3:09 pm

1 stop18h 59m

Ontario

sáb. 1/10

3:21 pm-11:39 am

1 stop18h 18m

$183

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

jue. 1/29

10:01 pm-1:32 pm

1 stop17h 31m

Ontario

dom. 2/1

5:21 pm-8:50 pm

1 stop25h 29m

$187

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

lun. 1/19

1:35 pm-5:44 pm

1 stop6h 09m

Ontario

lun. 1/26

1:05 pm-8:50 pm

1 stop5h 45m

$201

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

jue. 1/8

3:43 pm-9:23 pm

2 stops31h 40m

Ontario

jue. 1/15

10:18 pm-12:40 pm

1 stop12h 22m

$202

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

lun. 1/12

7:43 pm-11:56 pm

1 stop6h 13m

Ontario

jue. 1/15

10:18 pm-12:40 pm

1 stop12h 22m

$203

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

dom. 12/21

10:10 pm-9:17 pm

1 stop25h 07m

Ontario

sáb. 12/27

6:00 am-9:25 pm

1 stop13h 25m

$209

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 33m

Direct flights

None
The fastest flight from St. Louis to Ontario takes 5h 33m
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 33m 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 $137Free CancellationRating
5.8
3,084 reviews
Search Frontier flights
DeltaPriceFrom $171Free CancellationRating
7.9
8,008 reviews
Search Delta flights
American AirlinesPriceFrom $264Free CancellationRating
7.2
11,050 reviews
Search American Airlines flights
SouthwestPriceFrom $292Free CancellationRating
7.9
4,253 reviews
Search Southwest flights
United AirlinesPriceFrom $292Free CancellationRating
7.4
9,095 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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