Ontario (ONT) to St. Louis (STL) at a glance

Discover a range of airlines providing flights from Ontario (ONT) to St. Louis (STL) on this domestic short-haul route. Whether you prefer full-service options or cheap flights from Ontario, you can compare itineraries that align with your budget and travel schedule. Explore the iconic sights and neighborhoods of St. Louis while planning your journey from Los Angeles - Ontario International Airport (ONT) to Lambert-St. Louis International Airport (STL).

• Fastest flight duration: around 5h 15m non-stop
• Route distance: roughly 1,500 miles (2,410 km)
• Flights per week: around 15+ flights with multiple daily departures on average
• Typical fares (one-way): economy tickets often range from $90–$455, depending on seasonality and how far ahead you book

Flights from Los Angeles - Ontario International Airport (ONT) to Lambert-St. Louis International Airport (STL)

According to recent traveler bookings, here are the top airlines favored for flights from Ontario to St. Louis, including both non-stop and one-stop options. Popular layover locations include Denver International Airport (DEN, with a layover of about 1h 45m), Harry Reid International Airport (LAS, approximately 1h 15m), and Sky Harbor International Airport (PHX, around a 1-hour layover). These choices allow you to compare prices, total travel times, and cabin classes to craft the ideal itinerary for your journey.

• American Airlines: This full-service airline provides one-stop flights, holding around 30% of departures for the route. One-way fares generally fall between $140 and $505, with an in-flight duration of 4 hours and 30 minutes, leading to a total travel time of about 5 hours and 45 minutes, including layovers.
• Southwest Airlines: Known for its budget-friendly options, Southwest offers both non-stop and one-stop services, making up approximately 28% of route departures. One-way fares typically range from $130 to $495, with 4 hours and 30 minutes of flying time, resulting in a total journey of around 5 hours and 45 minutes.
• Frontier Airlines: As a low-cost carrier, Frontier provides one-stop service, accounting for about 22% of departures on this route. Fares for one-way journeys are usually between $90 and $245, with an in-flight time of 4 hours and 30 minutes, leading to a total travel duration of roughly 5 hours and 45 minutes, including layover.
• Delta: A reputable full-service airline, Delta offers one-stop flights, making up about 13% of departures for this route. Passengers can expect one-way fares ranging from $140 to $505, with an in-flight time of 4 hours and 30 minutes, totaling approximately 5 hours and 45 minutes of travel time, including layovers.
• United: Another full-service option, United provides one-stop service and constitutes roughly 7% of departures. One-way fares typically range from $140 to $470, with an in-flight duration of 4 hours and 30 minutes, leading to a total journey time of about 5 hours and 45 minutes, considering layover periods.

Travelers flying from Ontario to St. Louis can enhance their journey by upgrading their flight. United offers first class, while Delta provides options in both first class and premium economy class.

Best time to fly from Ontario (ONT) to St. Louis (STL)

The most popular months for travelers flying from Ontario to St. Louis are March, April, and June, when peak temperatures in St. Louis reach up to 76.1°F in June. If you prefer quieter travel, consider August, the least busy time to visit with temperatures around 77°F and typically the lowest average one-way fare (around $194). Flight availability peaks in May, June, and July, with approximately 21 flights per week, making it easier to find convenient departure times. December has the fewest flights, with approximately 12 flights per week.

• Cheapest time to fly: August usually offers good deals with average one-way fare around $194, roughly 14% cheaper than the yearly average.
• More budget-friendly months to fly: May and September typically offer average one-way fares of around $204.
• Most flight options: May, June, and July have the highest number of flights from Ontario to St. Louis, with approximately 21 flights per week, giving you more flexibility in scheduling your trip.

Month	Temperature	Demand	Weekly Flights	Average one-way Fare
January	31.6°F (-0.2°C)	Average	15	$251
February	34.9°F (1.6°C)	Average	15	$249
March	46.4°F (8.0°C)	Moderately High	17	$276
April	56.1°F (13.4°C)	Moderately High	17	$225
May	66.6°F (19.2°C)	Average	21	$201
June	76.1°F (24.5°C)	Moderately High	21	$226
July	78.6°F (25.9°C)	Average	21	$231
August	77.0°F (25.0°C)	Moderately Low	17	$194
September	70.9°F (21.6°C)	Moderately Low	17	$208
October	58.6°F (14.8°C)	Average	18	$217
November	46.2°F (7.9°C)	Average	17	$241
December	37.8°F (3.2°C)	Moderately Low	12	$218

*Average one-way fare is based on Expedia flight booking data from January 2025 to April 2026 for the specified route and travel class and may change depending on availability, dates, and demand.

Alternative route from Ontario (ONT) to St. Louis (STL)

• Orange County to St. Louis (SNA-STL): John Wayne Airport (SNA) is located approximately 31 miles from Los Angeles - Ontario International Airport (ONT). One-way economy ticket prices for this journey generally fall between $125 and $485, influenced by the time of year and when you make your reservation. Travelers can choose from both non-stop and one-stop flights, with common stopovers at Sky Harbor International Airport (PHX) and Denver International Airport (DEN). Major airlines operating on this route include American Airlines and the budget-friendly Southwest Airlines. Additionally, first-class service is offered on this route.

How to find the best prices for flights from Ontario (ONT) to St. Louis (STL)

Getting some of the best deals on flights from Ontario to St. Louis is all about timing and flexibility. Here are some key tips to help you save:

1. Best times to book and fly: cheaper fares are typically available when booking 2-8 weeks in advance, coinciding with when most travelers make their reservations. Early morning departures (12am-5am) usually offer lower prices, while morning flights (5am-12pm) are the most popular. Additionally, flying on Saturday generally results in cheaper rates, although Wednesday is the most traveled day.
2. Set up price alerts: stay updated on price changes by using Expedia's Price Tracker. Receive alerts when fares drop for your selected route.
3. Bundle and save: bundle your flight and hotel to save on Expedia, or unlock a hotel deal after booking your flight.*
4. Compare flight options: use Expedia's search tool to compare airlines, routes, direct vs. non-direct flights, and flight times. You can also sort by price to find the most affordable options.
5. Stay flexible with dates: being open to different travel days can sometimes help you find better prices on flights and hotels.
6. Think about luggage: nowadays, it's important to check the airline's baggage policies to find the best value. That may be paying for an additional carry-on bag or booking a ticket with checked luggage included. Either way, double-check your allowance before confirming your booking to avoid excess baggage fees at the airport.

*Members only. Savings vary and are not available on all bundles. Select hotels.

Arriving at Lambert-St. Louis International Airport from Los Angeles - Ontario International Airport

St. Louis welcomes travelers from Ontario with a range of transport options based on price, convenience, and proximity. Here's how to reach St. Louis efficiently:

• Hotel transfer: Transfers offer a convenient way to reach your hotel in St. Louis, with private rides that can be arranged in advance.
• Car rental: Renting a car from Lambert-St. Louis International Airport is a great option if you plan to explore and sightsee beyond the city. Browse cheap car rentals at Lambert-St. Louis International Airport on Expedia.
• Taxi/ride-hailing: Taxis and ride-hailing services may be available from designated pickup areas outside the terminal, check locally on arrival.
• Public transportation: From Lambert-St. Louis International Airport, Lambert Main Terminal Station, a metro station, is conveniently located just 0.1 miles away on foot, providing easy access for travelers.