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Uncover the best deals on Ontario to St Louis flights by comparing fares from hundreds of airlines and agencies.
Good to Know: Cheapest and Fastest ONT - STL Flights
Useful information for finding best airline tickets from Ontario International to Lambert St Louis International on your next trip.
Cheapest Round Trip Flight
$570
Frontier Airlines
• 1 stop
• 40h 8m
Jun 28 – Jul 05
The cheapest round trip flight from Ontario to St Louis (ONT-STL-ONT) is currently $570
Cheapest Direct Flight
$454
American Airlines
• nonstop
•
Jun 24
The cheapest nonstop flight from Ontario to St Louis (ONT-STL) is currently $454
Fastest Flight
5h 40m
The fastest nonstop flight from Ontario to St Louis (ONT-STL) takes 5h 40m
Top Airlines Flying from Ontario to St Louis
Latest Flight Deals from Ontario (ONT) to St Louis (STL)
Compare and book low fare round-trip air tickets from Ontario to St Louis. Ideal for travelers with confirmed return itineraries.
Jun 28 - Jul 05, Economy
Ontario → St Louis
40h 8m
11:58 AM - 2:06 PM • 1 stop
Ontario → St Louis
6h 49m
6:37 AM - 8:46 AM • nonstop
Frontier Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
15h 51m
12:08 PM - 11:59 PM • 1 stop
Ontario → St Louis
15h 7m
6:02 AM - 1:09 PM • 1 stop
Alaska Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
25h 20m
9:30 PM - 2:50 PM • 2 stops
Ontario → St Louis
8h 55m
5:45 AM - 9:20 AM • 1 stop
Southwest Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
12h 30m
9:40 PM - 7:30 AM • 1 stop
Ontario → St Louis
15h
6:00 AM - 1:00 PM • 2 stops
Southwest Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
13h 35m
11:55 AM - 10:10 PM • 1 stop
Ontario → St Louis
10h 30m
8:30 AM - 1:00 PM • 2 stops
Southwest Airlines
Flying to St Louis soon? We've surfaced some of the most affordable last-minute flights from Ontario to St Louis, ideal for urgent plans or spontaneous trips.
Jun 28 - Jul 05, Economy
Ontario → St Louis
40h 8m
11:58 AM - 2:06 PM • 1 stop
Ontario → St Louis
6h 49m
6:37 AM - 8:46 AM • nonstop
Frontier Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
15h 51m
12:08 PM - 11:59 PM • 1 stop
Ontario → St Louis
15h 7m
6:02 AM - 1:09 PM • 1 stop
Alaska Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
25h 20m
9:30 PM - 2:50 PM • 2 stops
Ontario → St Louis
8h 55m
5:45 AM - 9:20 AM • 1 stop
Southwest Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
12h 30m
9:40 PM - 7:30 AM • 1 stop
Ontario → St Louis
15h
6:00 AM - 1:00 PM • 2 stops
Southwest Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
13h 35m
11:55 AM - 10:10 PM • 1 stop
Ontario → St Louis
10h 30m
8:30 AM - 1:00 PM • 2 stops
Southwest Airlines
Looking for the fastest way to St Louis? These direct flight options from ONT to STL offer both convenience and value—no layovers, just straight to your destination.
Jun 24 - Jul 01, Economy
Ontario → St Louis
- • nonstop
Ontario → St Louis
- • nonstop
American Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
- • nonstop
Ontario → St Louis
- • nonstop
American Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
- • nonstop
Ontario → St Louis
- • nonstop
Alaska Airlines
Jul 01 - Jul 01, Economy
Ontario → St Louis
5h 40m
5:00 AM - 10:40 AM • nonstop
Ontario → St Louis
5h 50m
9:20 PM - 11:10 PM • nonstop
Southwest Airlines
Jun 28 - Jul 05, Economy
Ontario → St Louis
5h 40m
5:30 AM - 11:10 AM • nonstop
Ontario → St Louis
5h 55m
10:50 PM - 12:45 AM • nonstop
Southwest Airlines
FAQs on Ontario to St Louis Flights
What are the airports in Ontario?
ONT
What’s the most popular airline flying from ONT to STL?
The most popular airline flying from Ontario to St Louis are
Can I fly from ONT to STL non-stop?
Yes, you can fly ONT to STL non-stop on
Which airlines fly nonstop between Ontario and St Louis?
The non-stop flights between Ontario and St Louis are .
What’s the earliest departure time from ONT to STL Airport?
The earliest flight leaves ONT at 5:00 am and lands in STL - Lambert St Louis International
What are the airports in St Louis?
STL
Can I make changes to my Ontario to St Louis flight tickets or cancel them on FareLeaders.com?
No. We are an airfare comparison site. All the tickets are booked by the travel agent offering the flight deal and any changes or cancellations to be made are directly done directly by them or the airlines.
Can I cancel my flight tickets from ONT to STL?
Read the fare rules of the Ontario to St Louis air tickets booked. Some airlines allow you to cancel the tickets within a stipulated time period with a cancellation fee.
Which airline alliances offer flights from Ontario and St Louis?
operate flights between Ontario and St Louis
How long does a flight from Ontario to St Louis take?
It takes approximately 4 hour to fly non-stop from ONT to STL, which is 1545.85 miles by air.
Which airlines provide the cheapest flights from Ontario (ONT) to St Louis (STL) ?
In the past couple of days, the cheapest tickets to STL from ONT were found on F9 : USD 948
Do I need a passport to fly between ONT and STL?
No
What’s the latest departure time from ONT to STL ?
The last flight leaves ONT at 6:1600 pm
Ontario (ONT) to St Louis (STL): Airport Information
| Origin Airport | Ontario International , Ontario, US |
| Destination Airport | Lambert St Louis International , St Louis, US |
| Distance | 1546 miles |
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