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Cheap flights from St. Louis to Los Angeles from $119

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 8/9. 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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Find the cheapest flights from St. Louis to Los Angeles

Cheap round-trip flights

Frontier Logo
7:54 pm - 11:50 pmSTL-ONT
5h 56m1 stop
Frontier Logo
12:59 am - 9:11 amONT-STL
6h 12m1 stop
$204Frontier
Find Deal
Thu, Aug 21 - Sun, Aug 24
Frontier Logo
7:54 pm - 11:50 pmSTL-ONT
5h 56m1 stop
Frontier Logo
12:59 am - 9:11 amONT-STL
6h 12m1 stop
$230Frontier
Find Deal
Thu, Aug 21 - Mon, Aug 25
Frontier Logo
7:54 pm - 11:50 pmSTL-ONT
5h 56m1 stop
Frontier Logo
8:59 pm - 9:06 amONT-STL
10h 07m1 stop
$235Frontier
Find Deal
Mon, Sep 1 - Sun, Sep 7
Frontier Logo
7:55 pm - 7:54 pmSTL-ONT
25h 59m1 stop
Frontier Logo
8:59 pm - 9:06 amONT-STL
10h 07m1 stop
$237Frontier
Find Deal
Thu, Sep 4 - Fri, Sep 19
Frontier Logo
7:29 pm - 11:50 pmSTL-ONT
6h 21m1 stop
Frontier Logo
12:59 am - 9:11 amONT-STL
6h 12m1 stop
$240Frontier
Find Deal
Fri, Aug 15 - Wed, Aug 20
Frontier Logo
10:39 am - 3:24 pmSTL-ONT
6h 45m1 stop
Frontier Logo
8:59 pm - 9:06 amONT-STL
10h 07m1 stop
$241Frontier
Find Deal
Thu, Sep 4 - Sat, Sep 20
Frontier Logo
7:55 pm - 9:57 amSTL-ONT
16h 02m1 stop
Frontier Logo
6:56 pm - 9:07 amONT-STL
12h 11m1 stop
$243Frontier
Find Deal
Thu, Oct 2 - Sun, Oct 5
Frontier Logo
7:29 pm - 11:50 pmSTL-ONT
6h 21m1 stop
Frontier Logo
12:59 am - 9:11 amONT-STL
6h 12m1 stop
$244Frontier
Find Deal
Sat, Aug 16 - Fri, Aug 22
Frontier Logo
7:29 pm - 11:50 pmSTL-ONT
6h 21m1 stop
Frontier Logo
5:21 pm - 9:11 amONT-STL
13h 50m1 stop
$245Frontier
Find Deal
Wed, Aug 13 - Fri, Aug 15
Frontier Logo
2:27 pm - 8:52 pmSTL-ONT
8h 25m1 stop
Frontier Logo
5:21 pm - 9:11 amONT-STL
13h 50m1 stop
$250Frontier
Find Deal
Thu, Aug 7 - Tue, Aug 12

Frontier flights from St. Louis to Ontario

Our best Frontier deals on St. Louis to Ontario flight tickets
Frontier
Aug 21
STL7:54 pmLambert-St Louis
5h 56m
1 stop
ONT11:50 pmOntario
Aug 24
ONT12:59 amOntario
6h 12m
1 stop
STL9:11 amLambert-St Louis
$204
Find similar
Frontier
Aug 21
STL7:54 pmLambert-St Louis
5h 56m
1 stop
ONT11:50 pmOntario
Aug 25
ONT12:59 amOntario
6h 12m
1 stop
STL9:11 amLambert-St Louis
$230
Find similar
Frontier
Sep 1
STL7:54 pmLambert-St Louis
5h 56m
1 stop
ONT11:50 pmOntario
Sep 7
ONT8:59 pmOntario
10h 07m
1 stop
STL9:06 amLambert-St Louis
$235
Find similar

See travel insights to Los Angeles from

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 August instead. Flights to Ontario in August, while not as cheap as those in February, still average around $326.

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 $365 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 July 2025, prices for St. Louis to Ontario flights are approximately 51% 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

Best Price Found

$119

Fastest flight time

5h 56m

Direct flights

None

Airports in Ontario

1 airport
The best one-way flight to Ontario from St. Louis in the past 72 hours is $119. The best round-trip flight deal from St. Louis to Ontario found on momondo in the last 72 hours is $204.
The fastest flight from St. Louis to Ontario takes 5h 56m
There are no direct flights from St. Louis to Ontario. Popular non-direct route for this connection is Lambert-St Louis Airport - Ontario Airport.
There is 1 airport near Ontario: Ontario (ONT)
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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 56m 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
5.9
3,260 reviews
Search Frontier flights
DeltaPriceFrom $181Free CancellationRating
8.0
7,953 reviews
Search Delta flights
American AirlinesPriceFrom $281Free CancellationRating
7.2
10,000 reviews
Search American Airlines flights
SouthwestPriceFrom $341Free CancellationRating
8.0
4,243 reviews
Search Southwest flights
United AirlinesPriceFrom $344Free CancellationRating
7.4
8,856 reviews
Search United Airlines flights

  • Southwest Flights From St. Louis to Ontario

    Southwest operates around 4 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 $341 round-trip. Southwest has been scored 8.0/10 in 4,244 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.

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