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

View $90 flight on Tue, Sep 9, 2025Opens in a new window

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

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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 $189 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

United
Tue, Sep 9 - Thu, Sep 11
IAD
Washington
STL
St. Louis
$189 Roundtrip, found 5 days ago
$189
Roundtrip
found 5 days ago
Select United flight, departing Tue, Sep 9 from Washington to St. Louis, returning Thu, Sep 11, priced at $189 found 5 days ago
United
Sat, Sep 6 - Sat, Sep 13
IAD
Washington
STL
St. Louis
$190 Roundtrip, found 5 days ago
$190
Roundtrip
found 5 days ago
Select United flight, departing Sat, Sep 6 from Washington to St. Louis, returning Sat, Sep 13, priced at $190 found 5 days ago
Southwest Airlines
Sat, Oct 18 - Sat, Oct 25
IAD
Washington
STL
St. Louis
$199 Roundtrip, found 5 days ago
$199
Roundtrip
found 5 days ago
Select Southwest Airlines flight, departing Sat, Oct 18 from Washington to St. Louis, returning Sat, Oct 25, priced at $199 found 5 days ago
Delta
Mon, Sep 15 - Wed, Sep 17
IAD
Washington
STL
St. Louis
$201 Roundtrip, found 4 days ago
$201
Roundtrip
found 4 days ago
Select Delta flight, departing Mon, Sep 15 from Washington to St. Louis, returning Wed, Sep 17, priced at $201 found 4 days ago
United
Sat, Sep 6 - Sat, Sep 13
IAD
Washington
STL
St. Louis
$206 Roundtrip, found 5 days ago
$206
Roundtrip
found 5 days ago
Select United flight, departing Sat, Sep 6 from Washington to St. Louis, returning Sat, Sep 13, priced at $206 found 5 days ago
Southwest Airlines
Fri, Sep 5 - Tue, Sep 9
IAD
Washington
STL
St. Louis
$216 Roundtrip, found 5 days ago
$216
Roundtrip
found 5 days ago
Select Southwest Airlines flight, departing Fri, Sep 5 from Washington to St. Louis, returning Tue, Sep 9, priced at $216 found 5 days ago
United
Sat, Nov 1 - Tue, Nov 4
IAD
Washington
STL
St. Louis
$216 Roundtrip, found 5 days ago
$216
Roundtrip
found 5 days ago
Select United flight, departing Sat, Nov 1 from Washington to St. Louis, returning Tue, Nov 4, priced at $216 found 5 days ago
United
Sat, Nov 1 - Tue, Nov 4
IAD
Washington
STL
St. Louis
$218 Roundtrip, found 5 days ago
$218
Roundtrip
found 5 days ago
Select United flight, departing Sat, Nov 1 from Washington to St. Louis, returning Tue, Nov 4, priced at $218 found 5 days ago
Frontier Airlines
Fri, Aug 29 - Tue, Sep 2
IAD
Washington
STL
St. Louis
$233 Roundtrip, found 6 hours ago
$233
Roundtrip
found 6 hours ago
Select Frontier Airlines flight, departing Fri, Aug 29 from Washington to St. Louis, returning Tue, Sep 2, priced at $233 found 6 hours ago
American Airlines
Sat, Oct 18 - Sat, Oct 25
IAD
Washington
STL
St. Louis
$234 Roundtrip, found 5 days ago
$234
Roundtrip
found 5 days ago
Select American Airlines flight, departing Sat, Oct 18 from Washington to St. Louis, returning Sat, Oct 25, priced at $234 found 5 days ago

Find the cheapest month to fly from Washington (IAD) to St. Louis (STL)

March is typically the cheapest month to fly

From $160 - $512 per traveler.

Graph displaying average flight prices per month

Alternative airports near St. Louis

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

Select flight to Lambert-St. Louis Intl. STL. Cheapest option available. Average driving time to city center is 20 minutes. Flights from $339
STL
Lambert-St. Louis Intl.
Cheapest
Average driving time to city center20 min
Flights from $339
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
$189
Distance
694 mi
Average flight time
1 hour 20 mins

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 September. 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 $181 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 August 16 2025 and touching down at STL. The price was last updated on July 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 $90. This fare is based on the lowest price found on Expedia departing within the next three months. The flight takes off from IAD on August 31 2025. Prices were last updated on July 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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