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Cheap flights from St. Louis to Los Angeles from $61

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 2/9. 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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Cheap round-trip flights

Enter your travel dates to find the best prices.
Frontier Logo
4:51 pm - 7:07 amSTL-ONT
16h 16m1 stop
Frontier Logo
8:45 am - 9:07 amONT-STL
22h 22m1 stop
$170Frontier
Find Deal
Sat, Nov 8 - Tue, Nov 11
Frontier Logo
7:45 pm - 9:27 pmSTL-ONT
27h 42m1 stop
Frontier Logo
7:44 pm - 8:12 pmONT-STL
22h 28m1 stop
$172Frontier
Find Deal
Tue, Nov 4 - Thu, Nov 6
Frontier Logo
7:43 pm - 3:06 pmSTL-ONT
21h 23m1 stop
Frontier Logo
3:20 pm - 10:14 amONT-STL
16h 54m1 stop
$173Frontier
Find Deal
Sat, Dec 6 - Fri, Dec 12
Frontier Logo
7:43 pm - 3:06 pmSTL-ONT
21h 23m1 stop
Frontier Logo
6:15 am - 11:22 amONT-STL
27h 07m2 stops
$179Frontier
Find Deal
Sat, Dec 6 - Thu, Dec 11
Frontier Logo
7:43 pm - 11:09 amSTL-ONT
17h 26m1 stop
Frontier Logo
4:01 pm - 10:14 amONT-STL
16h 13m1 stop
$181Frontier
Find Deal
Wed, Dec 3 - Sun, Dec 7
Frontier Logo
7:45 pm - 9:27 pmSTL-ONT
27h 42m1 stop
Frontier Logo
8:45 am - 9:07 amONT-STL
22h 22m1 stop
$183Frontier
Find Deal
Tue, Nov 4 - Tue, Nov 11
Frontier Logo
7:43 pm - 11:09 amSTL-ONT
17h 26m1 stop
Frontier Logo
12:30 pm - 11:07 amONT-STL
44h 37m2 stops
$192Frontier
Find Deal
Wed, Dec 3 - Tue, Dec 9
Frontier Logo
7:45 pm - 9:27 pmSTL-ONT
27h 42m1 stop
Frontier Logo
4:05 pm - 9:07 amONT-STL
15h 02m1 stop
$193Frontier
Find Deal
Tue, Nov 4 - Fri, Nov 7
American Airlines Logo
11:35 am - 10:28 pmSTL-ONT
12h 53m1 stop
American Airlines Logo
12:55 pm - 11:56 pmONT-STL
9h 01m1 stop
$229American Airlines
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Tue, Dec 9 - Sat, Dec 13
Multiple Airlines Logo
7:43 pm - 3:06 pmSTL-ONT
21h 23m1 stop
Multiple Airlines Logo
6:15 am - 11:07 amONT-STL
26h 52m2 stops
$233Multiple Airlines
Find Deal
Sat, Dec 6 - Wed, Dec 10

Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Nov 8
STL4:51 pmLambert-St Louis
16h 16m
1 stop
ONT7:07 amOntario
Nov 11
ONT8:45 amOntario
22h 22m
1 stop
STL9:07 amLambert-St Louis
$170
Find similar
Frontier
Nov 4
STL7:45 pmLambert-St Louis
27h 42m
1 stop
ONT9:27 pmOntario
Nov 6
ONT7:44 pmOntario
22h 28m
1 stop
STL8:12 pmLambert-St Louis
$172
Find similar
Frontier
Dec 6
STL7:43 pmLambert-St Louis
21h 23m
1 stop
ONT3:06 pmOntario
Dec 12
ONT3:20 pmOntario
16h 54m
1 stop
STL10:14 amLambert-St Louis
$173
Find similar

American Airlines flights from St. Louis to Ontario

Our best American Airlines deals on St. Louis to Ontario flight tickets
American Airlines
Dec 9
STL11:35 amLambert-St Louis
12h 53m
1 stop
ONT10:28 pmOntario
Dec 13
ONT12:55 pmOntario
9h 01m
1 stop
STL11:56 pmLambert-St Louis
$229
Find similar
American Airlines
Oct 31
STL12:51 pmLambert-St Louis
10h 42m
1 stop
ONT9:33 pmOntario
Nov 1
ONT12:59 amOntario
8h 40m
1 stop
STL10:39 amLambert-St Louis
$520
Find similar
American Airlines
Oct 31
STL10:10 amLambert-St Louis
10h 25m
2 stops
ONT6:35 pmOntario
Nov 2
ONT9:59 amOntario
11h 51m
1 stop
STL11:50 pmLambert-St Louis
$524
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 October 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 11/8

4:51 pm-7:07 am

1 stop16h 16m

Ontario

Tue 11/11

8:45 am-9:07 am

1 stop22h 22m

$170

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 11/4

7:45 pm-9:27 pm

1 stop27h 42m

Ontario

Thu 11/6

7:44 pm-8:12 pm

1 stop22h 28m

$172

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 12/6

7:43 pm-3:06 pm

1 stop21h 23m

Ontario

Fri 12/12

3:20 pm-10:14 am

1 stop16h 54m

$173

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 12/6

7:43 pm-3:06 pm

1 stop21h 23m

Ontario

Thu 12/11

6:15 am-11:22 am

2 stops27h 07m

$179

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 12/3

7:43 pm-11:09 am

1 stop17h 26m

Ontario

Sun 12/7

4:01 pm-10:14 am

1 stop16h 13m

$181

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 11/4

7:45 pm-9:27 pm

1 stop27h 42m

Ontario

Tue 11/11

8:45 am-9:07 am

1 stop22h 22m

$183

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 12/3

7:43 pm-11:09 am

1 stop17h 26m

Ontario

Tue 12/9

12:30 pm-11:07 am

2 stops44h 37m

$192

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 11/4

7:45 pm-9:27 pm

1 stop27h 42m

Ontario

Fri 11/7

4:05 pm-9:07 am

1 stop15h 02m

$193

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 12/9

11:35 am-10:28 pm

1 stop12h 53m

Ontario

Sat 12/13

12:55 pm-11:56 pm

1 stop9h 01m

$229

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 12/6

7:43 pm-3:06 pm

1 stop21h 23m

Ontario

Wed 12/10

6:15 am-11:07 am

2 stops26h 52m

$233

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 $213. If you aren’t able to travel during the month of February, then book flights to Ontario from St. Louis during November instead. Flights to Ontario in November, while not as cheap as those in February, still average around $298.

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 October 2025, prices for St. Louis to Ontario flights are approximately 1% 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. 6h 05m 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
3,128 reviews
Search Frontier flights
DeltaPriceFrom $171Free CancellationRating
7.9
7,982 reviews
Search Delta flights
American AirlinesPriceFrom $264Free CancellationRating
7.2
11,032 reviews
Search American Airlines flights
SouthwestPriceFrom $292Free CancellationRating
8.0
4,236 reviews
Search Southwest flights
United AirlinesPriceFrom $292Free CancellationRating
7.4
8,995 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

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