$240 Cheap Flights from St. Louis (STL) to Sidney (SDY)

View $240 flight on Sun, Oct 12, 2025Opens in a new window

Popular airlines from St. Louis Lambert Intl. Airport (STL) to Sidney, MT (SDY-Sidney-Richland Municipal)

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Cheap Flights from St. Louis to Sidney (STL-SDY)

Prices were available within the past 7 days and start at $240 for one-way flights and $480 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Delta
Sun, Nov 2 - Mon, Nov 3
STL
St. Louis
SDY
Sidney
$480 Roundtrip, found 4 days ago
$480
Roundtrip
found 4 days ago
Select Delta flight, departing Sun, Nov 2 from St. Louis to Sidney, returning Mon, Nov 3, priced at $480 found 4 days ago
Delta
Mon, Oct 13 - Tue, Oct 14
STL
St. Louis
SDY
Sidney
$499 Roundtrip, found 5 days ago
$499
Roundtrip
found 5 days ago
Select Delta flight, departing Mon, Oct 13 from St. Louis to Sidney, returning Tue, Oct 14, priced at $499 found 5 days ago
United
Sun, Oct 12 - Sat, Oct 25
STL
St. Louis
SDY
Sidney
$529 Roundtrip, found 1 day ago
$529
Roundtrip
found 1 day ago
Select United flight, departing Sun, Oct 12 from St. Louis to Sidney, returning Sat, Oct 25, priced at $529 found 1 day ago
Delta
Mon, Oct 13 - Sun, Oct 19
STL
St. Louis
SDY
Sidney
$537 Roundtrip, found 5 days ago
$537
Roundtrip
found 5 days ago
Select Delta flight, departing Mon, Oct 13 from St. Louis to Sidney, returning Sun, Oct 19, priced at $537 found 5 days ago
Delta
Sun, Nov 2 - Thu, Nov 6
STL
St. Louis
SDY
Sidney
$539 Roundtrip, found 4 days ago
$539
Roundtrip
found 4 days ago
Select Delta flight, departing Sun, Nov 2 from St. Louis to Sidney, returning Thu, Nov 6, priced at $539 found 4 days ago
United
Tue, Oct 14 - Wed, Oct 15
STL
St. Louis
SDY
Sidney
$543 Roundtrip, found 5 days ago
$543
Roundtrip
found 5 days ago
Select United flight, departing Tue, Oct 14 from St. Louis to Sidney, returning Wed, Oct 15, priced at $543 found 5 days ago
Delta
Sat, Oct 11 - Thu, Oct 23
STL
St. Louis
SDY
Sidney
$544 Roundtrip, found 1 day ago
$544
Roundtrip
found 1 day ago
Select Delta flight, departing Sat, Oct 11 from St. Louis to Sidney, returning Thu, Oct 23, priced at $544 found 1 day ago
United
Sat, Oct 11 - Sat, Oct 18
STL
St. Louis
SDY
Sidney
$554 Roundtrip, found 1 day ago
$554
Roundtrip
found 1 day ago
Select United flight, departing Sat, Oct 11 from St. Louis to Sidney, returning Sat, Oct 18, priced at $554 found 1 day ago
United
Sun, Oct 12 - Fri, Oct 17
STL
St. Louis
SDY
Sidney
$557 Roundtrip, found 5 days ago
$557
Roundtrip
found 5 days ago
Select United flight, departing Sun, Oct 12 from St. Louis to Sidney, returning Fri, Oct 17, priced at $557 found 5 days ago
Hawaiian Airlines
Thu, Nov 6 - Fri, Nov 7
STL
St. Louis
SDY
Sidney
$565 Roundtrip, found 4 days ago
$565
Roundtrip
found 4 days ago
Select Hawaiian Airlines flight, departing Thu, Nov 6 from St. Louis to Sidney, returning Fri, Nov 7, priced at $565 found 4 days ago

Alternative airports near Sidney

Prices were available within the past 7 days. Prices and availability are subject to change.

Select flight to Sidney-Richland Municipal SDY. Cheapest and Closest option available. Average driving time to city center is 3 minutes. Flights from $529
SDY
Sidney-Richland Municipal
CheapestClosest
Average driving time to city center3 min
Flights from $529

Frequently asked questions

How much does a flight from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY) cost?
Grab a cheap one-way flight from $240 or cheap return flight from $480 from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY) with Expedia. Enter your travel dates and sort by "Price (lowest to highest)" to find our cheapest flight deals on this route.
What is the cheapest month to fly from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY)?
November is the least expensive month to fly from STL to SDY. Traveling outside of peak seasons is often the key to scoring lower fares.
What is the cheapest airline that flies from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY)?
Use the filter tool on Expedia to compare airlines and find the most affordable carrier that'll take you from STL to SDY. Then, sort your results by "Price (lowest to highest)" to pick up a great deal.
How many flights per day from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY)?
Direct flights from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY) aren't available daily, so you'll need to take a flight with a layover. Explore your options with Expedia's filters. Enter your dates and select either "1 Stop" or "2+ Stops."
What day of the week has the most flights from STL to SDY?
You'll usually find Tuesday the quietest day for flights, while Fridays tend to be the busiest.* However this can vary from season to season and during public holidays or peak travel times.*Busiest/quietest day to travel is based on Expedia flight demand through January to December 2024.
What is the best time to fly from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY)?
To land at Sidney-Richland Municipal Airport (SDY) without delays, pick a flight that leaves from Lambert-St. Louis Intl. Airport (STL) before 3 PM. The chance of cancellations is 22% higher, on average, for departures after this hour.**Most reliable time of the day and month to travel recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.
Is it cheaper to buy a plane ticket from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY) last-minute?
Last-minute fares from STL to SDY are typically more expensive. To secure the best rates, start looking for flights early. That said, if you're flexible with your travel plans, you may find a cheap ticket just before your departure.
Is it cheaper to book a STL to SDY flight and hotel package?
Securing a STL to SDY flight and hotel package is usually cheaper than booking separately. With Expedia, you can enjoy the ease of organizing your travels all in one place. Choose from our wide range of stays and then add flights, car rentals and activities to your booking. Bundle it all together, and you could save hundreds of dollars.
Can I cancel or change the date of my flight from Lambert-St. Louis Intl. Airport (STL) to Sidney-Richland Municipal Airport (SDY)?
If you booked your STL to SDY flight in the last 24 hours, you may be able to cancel or modify it without any fees. Depending on the airline and the type of fare you purchased, additional charges may apply for changes beyond that time. Airline policies and contact information can be found in your itinerary or confirmation email. Or, head to our Customer Service portal if you'd like more information.

Travel information

Travel information

Origin airport
Lambert-St. Louis Intl.
Destination airport
Sidney-Richland Municipal
Roundtrip price
$474
Distance
929 mi

Book with confidence

Book with confidence

St. Louis to Sidney Flights

The cheapest times to fly from St. Louis to Sidney

On average, Thursday can be the cheapest time to fly, according to data from the Airlines Reporting Corporation (ARC), one of the world's biggest databases for global airline sales. The data reveals that you could save up to 16% by flying on a Thursday—the cheapest day to travel on average—instead of a Sunday—the most expensive. Some of the most affordable flights from St. Louis to Sidney are during the month of November. You can find some of the cheapest flights from St. Louis to Sidney with Expedia's search tool and vast selection of airlines.

 

The best time to book a flight from St. Louis to Sidney

Sunday is one of the best days to book for cheap flights from St. Louis to Sidney: Tickets reserved on a Sunday cost between 6% and 13% less than those reserved on a Friday, according to ARC data. The data also suggests booking early can also lead to cheaper airfares. You could save 24% by buying your tickets for domestic flights at least a month in advance and 10% by booking international flights 2 months in advance.

 

How to find cheap round-trip tickets from St. Louis to Sidney

Being flexible with your dates and using Expedia's Price Drop Protection and Price Tracking features are some of the best ways of finding a cheap ticket from St. Louis to Sidney in 2025. You can also book with separate airlines for your outbound and return journeys, from $240 one-way. Expedia also offers Price Drop Protection, so if the cost of your airfare goes down after booking, you'll receive a credit for the difference*. This is available for a small fee, and is free to One Key Gold and Platinum tier members.

 

Expedia's Price Tracking feature means you can stay on top of airfares without manually checking every day. It sends you automated price alerts for cheap St. Louis to Sidney flights and uses historical data to indicate when the best time to book is. Download Expedia's free app to activate this handy tool in a few easy taps.

 

You could also save big by booking one of Expedia's vacation packages. Bundling together your St. Louis to Sidney airfare with your accommodations and car rental is often cheaper than booking everything separately. There’s also One Key, Expedia's generous rewards program. Join for free and you could earn One Key cash on most bookings to save on future adventures.

 

*Terms apply.

 

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

 

St. Louis to Sidney Flights

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*Available to One Key members.