STL - ONT

$100 Find Cheap Flights from St. Louis to Ontario - Compare and Save

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Everything you should know

Cheapest round-trip
$194
Typical prices: $303-$490
Frontier
Tue 2/27Fri 3/2
STL - ONT • 1 stop
Cheapest one-way
$100
Typical prices: $140-$305
Frontier
Sat 11/24
STL - ONT • 1 stop
Nonstop flights
Not available
There are currently no direct flights between St. Louis and Ontario. You'll need to take a connecting flight to reach the destination.
Insights
Insights
When to travel
November
Cheapest • 25% price drop
June
Most popular
Good to know
+1
Good to know
+1
Top layover airports
Salt Lake City (SLC)
Cheapest • Avg $385 (round-trip)
Phoenix Sky Harbor Intl (PHX)
Shortest trip • 5h 26m (one-way)
Insights
Insights
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Flight Deals
Booking Insights
Flight Deals

Cheap Flights from St. Louis to Ontario (STL-ONT)

 
Discover the best prices for you by selecting your travel dates on KAYAK.

Recent round-trip flight deals from St. Louis to Ontario

Sat, Feb 27 - Tue, Mar 2
Frontier Logo
7:02 pm - 12:05 amSTL  Lambert-St Louis-ONT Ontario
7h 03m1 stop Denver Intl
Frontier Logo
6:30 am - 10:20 amONT  Ontario-STL Lambert-St Louis
25h 50m1 stop Denver Intl
$194Frontier
Sat, Dec 12 - Sat, Jan 9
Frontier Logo
7:54 pm - 10:45 amSTL  Lambert-St Louis-ONT Ontario
16h 51m1 stop Denver Intl
Frontier Logo
3:33 pm - 9:37 pmONT  Ontario-STL Lambert-St Louis
28h 04m1 stop Las Vegas Harry Reid Intl
$214Frontier
Fri, Dec 11 - Mon, Jan 11
Multiple Airlines Logo
7:54 pm - 12:20 amSTL  Lambert-St Louis-ONT Ontario
6h 26m1 stop Denver Intl
Multiple Airlines Logo
4:16 pm - 2:56 pmONT  Ontario-STL Lambert-St Louis
20h 40m1 stop Seattle/Tacoma Intl
$261Multiple Airlines
Sat, Dec 12 - Sat, Jan 9
Southwest Logo
6:20 am - 9:50 amSTL  Lambert-St Louis-ONT Ontario
5h 30m1 stop Phoenix Sky Harbor Intl
Southwest Logo
5:35 am - 1:50 pmONT  Ontario-STL Lambert-St Louis
6h 15m1 stop Las Vegas Harry Reid Intl
$274Southwest
Thu, Dec 10 - Sat, Jan 9
Southwest Logo
8:25 am - 2:50 pmSTL  Lambert-St Louis-ONT Ontario
8h 25m1 stop Sacramento Intl
Southwest Logo
8:00 am - 4:05 pmONT  Ontario-STL Lambert-St Louis
6h 05m1 stop Las Vegas Harry Reid Intl
$279Southwest
Tue, Nov 17 - Tue, Nov 24
Delta Logo
7:00 pm - 11:49 pmSTL  Lambert-St Louis-ONT Ontario
6h 49m1 stop Salt Lake City
Delta Logo
1:15 pm - 9:18 pmONT  Ontario-STL Lambert-St Louis
6h 03m1 stop Salt Lake City
$279Delta
Sat, Dec 12 - Sat, Jan 9
American Airlines Logo
10:25 am - 4:20 pmSTL  Lambert-St Louis-ONT Ontario
7h 55m2 stops Dallas/Fort Worth Phoenix Sky Harbor Intl
American Airlines Logo
4:19 pm - 11:55 pmONT  Ontario-STL Lambert-St Louis
5h 36m1 stop Phoenix Sky Harbor Intl
$284American Airlines
Wed, Jan 20 - Mon, Jan 25
American Airlines Logo
8:47 am - 3:29 pmSTL  Lambert-St Louis-ONT Ontario
8h 42m2 stops Dallas/Fort Worth Phoenix Sky Harbor Intl
American Airlines Logo
4:19 pm - 11:55 pmONT  Ontario-STL Lambert-St Louis
5h 36m1 stop Phoenix Sky Harbor Intl
$284American Airlines
Thu, Dec 10 - Sat, Jan 9
United Airlines Logo
8:40 am - 5:36 pmSTL  Lambert-St Louis-ONT Ontario
10h 56m2 stops Denver Intl San Francisco
United Airlines Logo
5:00 am - 2:03 pmONT  Ontario-STL Lambert-St Louis
7h 03m1 stop Denver Intl
$284United Airlines
Wed, Dec 9 - Sat, Jan 9
United Airlines Logo
8:40 am - 5:36 pmSTL  Lambert-St Louis-ONT Ontario
10h 56m2 stops Denver Intl San Francisco
United Airlines Logo
5:00 am - 2:03 pmONT  Ontario-STL Lambert-St Louis
7h 03m1 stop Denver Intl
$284United Airlines
Booking Insights

Price, demand and travel trends for St. Louis to Ontario flights

Use KAYAK data on prices, travel dates, airlines and seasonal trends to compare options and book flights with more confidence.

How much is a round-trip flight from St. Louis to Ontario?

Round-trip flights from St. Louis to Ontario typically range from $303 to $490. The lowest price found in the past 5 days was $194, on Frontier.

What's the cheapest day of the week to fly from St. Louis to Ontario?

Based on deals KAYAK users found in the last 12 months, Tuesday is the cheapest day of the week to fly from St. Louis to Ontario. It’s 8% cheaper than the average day, while Sunday is the most expensive, with prices 73% higher.

What’s the cheapest month to fly from St. Louis to Ontario?

•November is the cheapest month to fly from St. Louis to Ontario at $292 round-trip.
•September ($561) and June ($510) are the most expensive months.
•The price difference between flying in the cheapest and most expensive months is 92% on average.
This is based on KAYAK aggregated and averaged internal data over the past 12 months.

Find deals

Key details for St. Louis to Ontario flights

Low season

September

Cheapest flight

$100
Beat the crowds with an average 34% drop in travelers.
The most popular month to fly with an average 36% increase in travelers.
One-way flight from St. Louis to Ontario

When to book flights from St. Louis to Ontario

Are your dates flexible? Find out the best times to travel from St. Louis to Ontario based on our flight data from the last year. Discover the cheapest month and even day to fly.
Estimated round-trip price

Your St. Louis to Ontario flight questions, answered

Find helpful answers about this route, including flight times, airports, airlines and booking tips.

  • What cabin classes can I book on flights from St. Louis to Ontario?

    Only Economy Class is available on flights from St. Louis to Ontario.

  • How long is a flight from St. Louis to Ontario?

    A nonstop flight from St. Louis to Ontario takes 00m, covering 1,541 miles.

  • Do I need a passport to fly from St. Louis to Ontario?

    No, a passport is not required for this domestic route, but you will need a real ID-compliant driver's license, a state ID or another TSA-accepted form of identification.

  • How much should I expect to pay for a St. Louis to Ontario flight?

    Round-trip flights from St. Louis to Ontario range from $303 to $490, with an average of $389 over the past 12 months. Anything below $303 counts as a good deal.

  • Have flight prices from St. Louis to Ontario changed much recently?

    Yes. Based on fares seen in the past 5 days, round-trip prices on this route showed a wide range, from about $194 to $1,363. That means the highest observed fare was about 7x higher than the lowest one.

  • How are flight prices from St. Louis to Ontario looking right now?

    One-way fares from St. Louis to Ontario are currently lower than usual. Average one-way flight prices are about $182, which is 10% below the typical average for this route.

  • What car rental options are available at Ontario Airport (ONT)?

    Ontario Airport (ONT) hosts 5 major car rental companies, with daily rates starting from around $18 for economy cars. Top options include:

    • Fox
    • Thrifty
    • Europcar
    • Dollar
    • Alamo

  • Which airports can I use when flying from St. Louis to Ontario?

    Flights from St. Louis to Ontario usually depart from Lambert-St Louis (STL) and arrive at Ontario (ONT).

  • Which airports do connecting flights from St. Louis to Ontario pass through?

    One-stop flights from St. Louis to Ontario most commonly connect through:

    • Denver Intl (DEN) - 53% of one-stop connections
    • Las Vegas Harry Reid Intl (LAS) - 15% of one-stop connections
    • Phoenix Sky Harbor Intl (PHX) - 14% of one-stop connections
    • Dallas/Fort Worth (DFW) - 10% of one-stop connections

  • Can I save money by using flexible dates for flights from St. Louis to Ontario?

    Yes. Flexible dates can save you up to 48% on flights from St. Louis to Ontario. Tuesday is the cheapest departure day at $358 round-trip on average, while Sunday is the most expensive at $676, a difference of $318.

    KAYAK's flexible dates feature shows options up to 3 days before and after your selected dates, making it easier to compare nearby fares.

  • How much time can I save by choosing a different layover airport from St. Louis to Ontario?

    Flying via Phoenix Sky Harbor Intl (PHX) gives the shortest average 1-stop total travel time at 5h 26m, compared with 5h 59m via Dallas Love Field (DAL) and 6h 01m via Salt Lake City (SLC).

  • What is the time difference between St. Louis and Ontario?

    Ontario is 2 hours behind St. Louis (Pacific Time vs Central Time). Plan for the time shift when scheduling connections or first-day activities.

  • What popular places can I visit in Ontario?

    Some of the most popular sights in Ontario are Ontario Convention Center and Cucamonga-Guasti Regional Park. These are among the most viewed places in Ontario on KAYAK.

Your guide to booking St. Louis to Ontario flights

Get tips on when to book, when to fly and what to know before your trip.
  • If your dates are flexible, aim for a Tuesday departure and avoid flying on Sunday. On this route, Tuesday flights average $358, about $318 less than Sunday fares (47% savings) based on the last 12 months.
  • If you can choose when to travel, plan your St. Louis to Ontario trip for November. Fares historically average $292 round-trip in that month - typically $269 less than the most expensive month, which is September (based on the last 12 months).
  • If you're arriving late at night and need somewhere to stay, check out these hotels close to Ontario Airport.

    • Ontario Airport Inn
    • Azure Hotel & Suites, Trademark Collection by Wyndham
    • Holiday Inn Ontario Airport By IHG

More options for your flight from St. Louis to Ontario

Complete your trip to Ontario with a hotel stay or car rental

Car rentals in Ontario
Hotels in Ontario
Vacations in Ontario