$90 Cheap Flights from Washington (IAD) to St. Louis (STL)

View $90 flight on Sun, Aug 31, 2025Opens in a new window

Popular airlines from Washington Dulles Intl. Airport (IAD) to St. Louis Lambert Intl. Airport (STL)

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Find available prices by choosing your travel dates.

Cheap Flights from Washington to St. Louis (IAD-STL)

Prices were available within the past 7 days and start at $90 for one-way flights and $188 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Frontier Airlines
Sat, Apr 26 - Wed, Apr 30
IAD
Washington
STL
St. Louis
$188 Roundtrip, found 1 day ago
$188
Roundtrip
found 1 day ago
Select Frontier Airlines flight, departing Sat, Apr 26 from Washington to St. Louis, returning Wed, Apr 30, priced at $188 found 1 day ago
United
Wed, May 28 - Thu, May 29
IAD
Washington
STL
St. Louis
$192 Roundtrip, found 1 day ago
$192
Roundtrip
found 1 day ago
Select United flight, departing Wed, May 28 from Washington to St. Louis, returning Thu, May 29, priced at $192 found 1 day ago
Frontier Airlines
Mon, May 5 - Wed, May 21
IAD
Washington
STL
St. Louis
$198 Roundtrip, found 9 hours ago
$198
Roundtrip
found 9 hours ago
Select Frontier Airlines flight, departing Mon, May 5 from Washington to St. Louis, returning Wed, May 21, priced at $198 found 9 hours ago
Delta
Thu, May 29 - Sat, May 31
IAD
Washington
STL
St. Louis
$202 Roundtrip, found 8 hours ago
$202
Roundtrip
found 8 hours ago
Select Delta flight, departing Thu, May 29 from Washington to St. Louis, returning Sat, May 31, priced at $202 found 8 hours ago
United
Tue, Jul 1 - Wed, Jul 2
IAD
Washington
STL
St. Louis
$204 Roundtrip, found 2 days ago
$204
Roundtrip
found 2 days ago
Select United flight, departing Tue, Jul 1 from Washington to St. Louis, returning Wed, Jul 2, priced at $204 found 2 days ago
United
Mon, Jun 30 - Tue, Jul 1
IAD
Washington
STL
St. Louis
$204 Roundtrip, found 1 day ago
$204
Roundtrip
found 1 day ago
Select United flight, departing Mon, Jun 30 from Washington to St. Louis, returning Tue, Jul 1, priced at $204 found 1 day ago
Frontier Airlines
Mon, May 5 - Thu, May 8
IAD
Washington
STL
St. Louis
$208 Roundtrip, found 16 hours ago
$208
Roundtrip
found 16 hours ago
Select Frontier Airlines flight, departing Mon, May 5 from Washington to St. Louis, returning Thu, May 8, priced at $208 found 16 hours ago
Frontier Airlines
Sun, May 25 - Fri, May 30
IAD
Washington
STL
St. Louis
$209 Roundtrip, found 6 hours ago
$209
Roundtrip
found 6 hours ago
Select Frontier Airlines flight, departing Sun, May 25 from Washington to St. Louis, returning Fri, May 30, priced at $209 found 6 hours ago
American Airlines
Sun, May 25 - Fri, May 30
IAD
Washington
STL
St. Louis
$232 Roundtrip, found 6 hours ago
$232
Roundtrip
found 6 hours ago
Select American Airlines flight, departing Sun, May 25 from Washington to St. Louis, returning Fri, May 30, priced at $232 found 6 hours ago
Southwest Airlines
Tue, Jun 24 - Sun, Jun 29
IAD
Washington
STL
St. Louis
$273 Roundtrip, found 6 hours ago
$273
Roundtrip
found 6 hours ago
Select Southwest Airlines flight, departing Tue, Jun 24 from Washington to St. Louis, returning Sun, Jun 29, priced at $273 found 6 hours ago
Flights from Washington (IAD) to St. Louis (STL)
Origin airport
Washington Dulles Intl.
Destination airport
Lambert-St. Louis Intl.
Airlines serving
American Airlines, Delta, Frontier Airlines, Southwest Airlines, United
Roundtrip price
$188
Distance
694 mi

Washington to St. Louis Flights

The cheapest times to fly from Washington to St. Louis

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 Washington to St. Louis are during the month of April. You can find some of the cheapest flights from Washington to St. Louis with Expedia's search tool and vast selection of airlines.

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

Sunday is one of the best days to book for cheap flights from Washington to St. Louis: 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 Washington to St. Louis

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 Washington to St. Louis in 2025. You can also book with separate airlines for your outbound and return journeys, from $90 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 Washington to St. Louis 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 Washington to St. Louis 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.

Frequently asked questions

How much does a flight from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL) cost?
You can pick up cheap return fares starting from $220 from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL). This information is based on the cheapest price found on Expedia for this return journey departing within the next three months. This airfare is for a United and Southwest Airlines flight leaving IAD on May 10 2025 and touching down at STL. The price was last updated on April 23 2025 and has not changed since.
What is the cheapest month to fly from IAD to STL?
The cheapest flights from IAD to STL are usually during off-peak season, when demand is lower. To save money, avoid flying during public holidays, school breaks and major local events.
Which airlines fly direct from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL)?
Jump on a nonstop flight with United Airlines and head straight from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL).
What is the cheapest airline that flies from IAD to STL?
Jet off from IAD to STL with United. This carrier currently has the lowest one-way fare for this route, starting from $140. This fare is based on the lowest price found on Expedia departing within the next three months. The flight takes off from IAD on June 30 2025. Prices were last updated on April 23 2025 and have not changed since.
How many flights per day from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL)?
When departing from Washington Dulles Intl. Airport (IAD), you can pick from an average of 2 daily nonstop flights to Lambert-St. Louis Intl. Airport (STL).
What are the most popular departure times for flights from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL)?
The 8 AM departures from IAD to STL are typically the busiest. They can also be more expensive. If you’re hoping to save money, pick a less crowded time to fly.
What day of the week has the most flights from IAD to STL?
Depart on a Friday if you’re searching for the biggest selection of flights from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL).
What is the earliest flight from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL)?
The earliest flight out of Washington Dulles Intl. Airport (IAD) is at around 8:50AM UTC-5. Catch this flight and you’ll arrive at Lambert-St. Louis Intl. Airport (STL) at approximately 10:24AM UTC-6. The total travel time is 2h 34m.
How long does it take to fly from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL)?
Flights from IAD to STL have an average travel time of 2 hours and 34 minutes. The distance between the two airports is 700 mi.
What is the best time to fly from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL)?
Select a flight from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL) that takes off before 3 PM to reduce the risk of delays and cancellations. Departures after this hour are on average 22% more likely to be canceled.**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.
What airports do you fly into for St. Louis from Washington Dulles Intl. Airport (IAD)?
Compare your flight options from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL). This is the only airport in St. Louis you can arrive at if you’re taking a direct flight.
Is it cheaper to buy a plane ticket from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL) last-minute?
Booking your ticket from IAD to STL shortly before your trip is typically more expensive. But if you’re flexible with your travel dates and times, you could bag a cheap last-minute fare.
Is it cheaper to book an IAD to STL flight and hotel package?
Compared with arranging hotels and flights separately, booking an IAD to STL flight and hotel package with Expedia could lead to significant savings. What’s more, having it all in one place will take the hassle out of travel planning. Just secure your flights and select from our wide range of hotels, then customize your trip with extras like tours, car rentals and activities.
Can I cancel or change the date of my flight from Washington Dulles Intl. Airport (IAD) to Lambert-St. Louis Intl. Airport (STL)?
In most cases, you can cancel or reschedule your IAD to STL flight. However, additional charges may apply, especially if you booked over 24 hours ago. Check your itinerary for the airline’s fees and rules on flight changes, or if you’d like more information, visit our Customer Service portal.

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*Available to One Key members.