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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
$399
Southwest Airlines
• 1 stop
• 12h 20m
Aug 01 – Aug 02
The cheapest round trip flight from Ontario to St Louis (ONT-STL-ONT) is currently $399
Cheapest One way Flight
$205
Southwest Airlines
• 2 stops
• 10h 35m
Jul 24
The cheapest one way flight from Ontario to St Louis (ONT-STL) is currently $205
Cheapest Direct Flight
$911
Southwest Airlines
• nonstop
• 5h 40m
Jul 17
The cheapest nonstop flight from Ontario to St Louis (ONT-STL) is currently $911
Fastest Flight
5h 35m
The fastest nonstop flight from Ontario to St Louis (ONT-STL) takes 5h 35m
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.
Aug 01 - Aug 02, Economy
Ontario → St Louis
12h 20m
3:00 PM - 12:40 AM • 1 stop
Ontario → St Louis
8h 55m
5:45 AM - 9:20 AM • 1 stop
Southwest Airlines
Aug 01 - Aug 02, Economy
Ontario → St Louis
12h 10m
2:20 PM - 11:50 PM • 1 stop
Ontario → St Louis
8h 55m
5:15 PM - 8:50 PM • 1 stop
Southwest Airlines
Aug 01 - Aug 02, Economy
Ontario → St Louis
10h 20m
6:00 AM - 2:20 PM • 1 stop
Ontario → St Louis
8h 55m
5:45 AM - 9:20 AM • 1 stop
Southwest Airlines
Aug 01 - Aug 02, Economy
Ontario → St Louis
10h
1:00 PM - 9:00 PM • 1 stop
Ontario → St Louis
9h 13m
7:55 PM - 11:48 PM • 1 stop
Delta Airlines
Aug 01 - Aug 02, Economy
Ontario → St Louis
23h 35m
7:05 AM - 11:20 PM • 1 stop
Ontario → St Louis
23h 50m
11:18 AM - 11:48 PM • 2 stops
Delta Airlines
Explore competitive one-way airfare options for ONT - STL flights. Best suited for flexible or open-ended travel plans.
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.
Jul 17 - Jul 25, Economy
Ontario → St Louis
8h 55m
4:40 PM - 12:15 AM • 1 stop
Ontario → St Louis
9h 15m
9:45 AM - 1:40 PM • 1 stop
Southwest Airlines
Jul 17 - Jul 25, Economy
Ontario → St Louis
13h 50m
8:00 AM - 6:30 PM • 1 stop
Ontario → St Louis
8h 45m
5:45 AM - 9:10 AM • 1 stop
Southwest Airlines
Jul 17 - Jul 25, Economy
Ontario → St Louis
13h 25m
6:00 AM - 4:05 PM • 1 stop
Ontario → St Louis
8h 40m
7:35 PM - 10:55 PM • 1 stop
Southwest Airlines
Jul 17 - Jul 25, Economy
Ontario → St Louis
10h 20m
4:20 PM - 12:40 AM • 1 stop
Ontario → St Louis
10h
1:50 PM - 5:50 PM • 1 stop
Southwest Airlines
Jul 17 - Jul 25, Economy
Ontario → St Louis
16h 45m
11:48 AM - 11:53 PM • 1 stop
Ontario → St Louis
10h 38m
6:00 AM - 10:38 AM • 1 stop
Delta 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.
Jul 17 - Jul 25, Economy
Ontario → St Louis
5h 40m
1:30 PM - 7:10 PM • nonstop
Ontario → St Louis
6h 40m
8:45 PM - 10:45 PM • 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 UA : USD 251
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 6:30 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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