$20 Cheap Flights to O'Fallon, IL

The cheapest day to fly

Get started finding a cheap flight to O'Fallon on Expedia by either choosing a deal on this page or entering into the search bar your travel dates, origin airport, and whether you want roundtrip or one-way airfare. You can filter for flexibility, number of stops, airline, and departure/arrival times to find the best flight for you.

The cheapest month to fly

January is the cheapest month to fly to O'Fallon. This coincides with the low season when fewer people travel. Whichever month you travel in, though, be sure to book at least a month in advance if you want to score cheap tickets to O'Fallon. ARC's data shows that domestic flights booked 28 days or more before departure are typically 24% cheaper than those booked last minute.

The most affordable time to book a flight

Typically, a Sunday can be the cheapest time to book a flight to O'Fallon, according to ARC’s data. On average, you could save between 6% and 13% by booking on a Sunday instead of a Friday, which is the most expensive day to make a reservation.

The cheapest round-trip tickets to O'Fallon

The lowest price for round-trip flights to O'Fallon in 2025 starts from from $54, while one-way tickets start from from $20. Expedia's effective search tool is one of the best ways to find a budget airfare. Simply enter your dates, and within seconds, it'll show you a vast selection of the cheapest flights to O'Fallon. If you have a preferred departure time or airline, you can use the handy filters to customize your search.

The cheapest airlines flying to O'Fallon

Frontier Airlines, American Airlines, Southwest Airlines, United, Spirit Airlines, Delta are just some of the airlines that can typically offer cheap tickets to O'Fallon. You can find their most affordable flights by using the “airline” search filter and then sorting prices from low to high. As a trusted partner of the world's leading airlines, Expedia offers you some of the best airfare deals to O'Fallon and countless more destinations worldwide.

The most affordable airports to fly into

To view the cheapest airports to fly into for O'Fallon, simply order your search results from lowest to highest price. Expedia's search tool compares flight prices for all airports close to your destination, so you don't have to manually search them one by one to find the cheapest flight to O'Fallon. If you have a preferred place to fly into, take advantage of the “arrival airport” filter to narrow down your search on Expedia.

Save with a package

With Expedia's amazing package deals, you could save hundreds of dollars by booking your O'Fallon plane tickets together with your accommodations, car rental, or activities. Just select the search wizard's “package” option to view some of the cheapest deals. Look out for the green savings label to see how much you're saving.

Date flexibility for the cheapest flights to O'Fallon

If you can be flexible with your travel dates, it's a good idea to broaden your search by comparing prices on different days. This will open up more options, meaning you could uncover a less expensive flight to O'Fallon.

Stopover savings

The cheapest tickets to O'Fallon are sometimes those with a stopover. Book one of these flights, and you'll change planes at an airport en route to O'Fallon. While the overall travel time might be longer than a non-stop flight, you may decide it's worth it for the money saved.

Get Expedia's Price Drop Protection

Price Drop Protection means that if your flight gets cheaper after booking, you'll be credited the difference*. This gives you peace of mind that you're getting one of the cheapest flights to O'Fallon for your chosen departure. Expedia's Price Drop Protection is available for a small fee but is free to One Key Gold and Platinum tier members.

*Terms apply.

Use our Price Tracking feature

Expedia's Price Tracking feature is another great tool that removes the guesswork from finding cheap flights to O'Fallon. Simply download the free Expedia app to your smart device and activate O'Fallon flight price alerts for your travel dates. There's even a price predictor tool that uses historical data to indicate the best time to book, giving you peace of mind that you'll nab the lowest prices.

Book with Expedia

As well as Price Drop Protection and Price Tracking, Expedia's close partnership with a vast selection of the world's leading airlines means you're sure to find cheap flights to O'Fallon. Plus, the One Key rewards program lets you earn real cash rewards on most bookings that you can use to save money on future trips. Best of all, it's free to join, and members often unlock exclusive discounts, too.

Disclaimer: ARC The statistics are based on average round-trip ticket prices between January and August 2023. The percentages you see are averages.