$104 Cheap Flights from St. Louis (STL) to Washington (IAD)

View $104 flight on Sat, Aug 16, 2025Opens in a new window

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

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

Prices were available within the past 7 days and start at $104 for one-way flights and $199 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Southwest Airlines
Mon, Sep 22 - Tue, Sep 30
STL
St. Louis
IAD
Washington
$199 Roundtrip, found 5 days ago
$199
Roundtrip
found 5 days ago
Select Southwest Airlines flight, departing Mon, Sep 22 from St. Louis to Washington, returning Tue, Sep 30, priced at $199 found 5 days ago
United
Wed, Aug 20 - Sat, Aug 23
STL
St. Louis
IAD
Washington
$206 Roundtrip, found 5 days ago
$206
Roundtrip
found 5 days ago
Select United flight, departing Wed, Aug 20 from St. Louis to Washington, returning Sat, Aug 23, priced at $206 found 5 days ago
Frontier Airlines
Sat, Aug 2 - Sat, Aug 9
STL
St. Louis
IAD
Washington
$208 Roundtrip, found 3 hours ago
$208
Roundtrip
found 3 hours ago
Select Frontier Airlines flight, departing Sat, Aug 2 from St. Louis to Washington, returning Sat, Aug 9, priced at $208 found 3 hours ago
Southwest Airlines
Mon, Sep 22 - Tue, Sep 30
STL
St. Louis
IAD
Washington
$214 Roundtrip, found 5 days ago
$214
Roundtrip
found 5 days ago
Select Southwest Airlines flight, departing Mon, Sep 22 from St. Louis to Washington, returning Tue, Sep 30, priced at $214 found 5 days ago
Frontier Airlines
Thu, Aug 21 - Sun, Aug 31
STL
St. Louis
IAD
Washington
$215 Roundtrip, found 5 days ago
$215
Roundtrip
found 5 days ago
Select Frontier Airlines flight, departing Thu, Aug 21 from St. Louis to Washington, returning Sun, Aug 31, priced at $215 found 5 days ago
United
Wed, Aug 20 - Sat, Aug 23
STL
St. Louis
IAD
Washington
$216 Roundtrip, found 5 days ago
$216
Roundtrip
found 5 days ago
Select United flight, departing Wed, Aug 20 from St. Louis to Washington, returning Sat, Aug 23, priced at $216 found 5 days ago
Frontier Airlines
Sat, Aug 2 - Thu, Aug 7
STL
St. Louis
IAD
Washington
$218 Roundtrip, found 3 hours ago
$218
Roundtrip
found 3 hours ago
Select Frontier Airlines flight, departing Sat, Aug 2 from St. Louis to Washington, returning Thu, Aug 7, priced at $218 found 3 hours ago
United
Fri, Aug 29 - Wed, Sep 3
STL
St. Louis
IAD
Washington
$220 Roundtrip, found 6 days ago
$220
Roundtrip
found 6 days ago
Select United flight, departing Fri, Aug 29 from St. Louis to Washington, returning Wed, Sep 3, priced at $220 found 6 days ago
Delta
Tue, Sep 2 - Sat, Sep 6
STL
St. Louis
IAD
Washington
$230 Roundtrip, found 1 day ago
$230
Roundtrip
found 1 day ago
Select Delta flight, departing Tue, Sep 2 from St. Louis to Washington, returning Sat, Sep 6, priced at $230 found 1 day ago
American Airlines
Wed, Sep 24 - Mon, Sep 29
STL
St. Louis
IAD
Washington
$271 Roundtrip, just found
$271
Roundtrip
just found
Select American Airlines flight, departing Wed, Sep 24 from St. Louis to Washington, returning Mon, Sep 29, priced at $271 just found

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

February is typically the cheapest month to fly

From $149 - $603 per traveler.

Graph displaying average flight prices per month

Alternative airports near Washington

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

Select flight to Ronald Reagan Washington National DCA. Closest option available. Average driving time to city center is 8 minutes. Flights from $421
DCA
Ronald Reagan Washington National
Closest
Average driving time to city center8 min
Flights from $421
Flights from St. Louis (STL) to Washington (IAD)
Origin airport
Lambert-St. Louis Intl.
Destination airport
Washington Dulles Intl.
Airlines serving
American Airlines, Delta, Frontier Airlines, Southwest Airlines, United
Roundtrip price
$198
Distance
694 mi
Average flight time
3 hours 8 mins

St. Louis to Washington Flights

The cheapest times to fly from St. Louis to Washington

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

 

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

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

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 Washington in 2025. You can also book with separate airlines for your outbound and return journeys, from $104 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 Washington 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 Washington 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 Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD) cost?
You can find cheap return fares from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD) starting from $179. Book a seat and start your adventure. 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 flight leaving STL on August 13 2025 and touching down at IAD. The price was last updated on July 23 2025 and has not changed since.
What is the cheapest month to fly from STL to IAD?
The cheapest flights from STL to IAD 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 Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD)?
Jump on a direct flight with United Airlines and fly straight from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD).
What is the cheapest airline that flies from STL to IAD?
With fares starting at $116 for a one-way journey from STL to IAD, United is currently the cheapest carrier flying this route. This fare is based on the lowest price found on Expedia departing within the next three months. The flight takes off from STL on August 9 2025. Prices were last updated on July 23 2025 and have not changed since.
How many flights per day from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD)?
When flying out of Lambert-St. Louis Intl. Airport (STL), you'll have a choice from an average of 2 daily nonstop flights to Washington Dulles Intl. Airport (IAD).
What are the most popular departure times for flights from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD)?
Flights between STL and IAD are busiest at 8 AM. If you'd like a more relaxed atmosphere and potentially cheaper prices, choose a departure that's outside typical rush times.
What day of the week has the most flights from STL to IAD?
Depart on a Friday if you're after the biggest selection of flights from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD).
What is the earliest flight from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD)?
The earliest flight jetting off from Lambert-St. Louis Intl. Airport (STL) is at around 8:15AM UTC-6. Board this plane and you'll reach Washington Dulles Intl. Airport (IAD) at approximately 11:33AM UTC-5. The total time in the air is 2h 18m.
How long does it take to fly from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD)?
The average flight time from STL to IAD is 2 hours and 13 minutes, covering a total distance of 700 mi.
What airline has the least delays from STL to IAD?
With 88% of flights typically arriving as scheduled, United Airlines has the best on-time performance for direct flights from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD). To monitor your flight status and get notified if anything changes, use the Expedia App.
What is the best time to fly from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD)?
To touch down at Washington Dulles Intl. Airport (IAD) on schedule, opt for a flight that leaves Lambert-St. Louis Intl. Airport (STL) before 3 PM. The likelihood of cancellations is 22% higher, on average, for departures after this time.**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 Washington from Lambert-St. Louis Intl. Airport (STL)?
You can land at one of these Washington airports after your direct flight from Lambert-St. Louis Intl. Airport (STL):

  • Ronald Reagan Washington National Airport (DCA)
  • Washington Dulles Intl. Airport (IAD)
  • Baltimore Washington Intl. Thurgood Marshall Airport (BWI)

Is it cheaper to buy a plane ticket from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD) last-minute?
Last-minute bookings from STL to IAD are usually more expensive. To secure the best prices, start searching for flights ahead of time. That said, if you're flexible with your travel dates, you may find a cheap fare right before you leave.
Is it cheaper to book a STL to IAD flight and hotel package?
You'll generally save money by booking a STL to IAD flight and hotel package compared to booking separately. In fact, you could save hundreds of dollars by bundling with Expedia. And it's easy to manage everything in one convenient place. After selecting your ideal accommodations and flights, consider other add-ons like car rentals, tours and activities.
Can I cancel or change the date of my flight from Lambert-St. Louis Intl. Airport (STL) to Washington Dulles Intl. Airport (IAD)?
If you booked your STL to IAD flight within the last 24 hours, you may be able to modify or cancel it at no cost. Depending on the airline and the ticket type you purchased, additional charges may apply for changes after that time. Airline policies and contact information can be found in your itinerary or confirmation email. Or, go to our Customer Service portal if you'd like more information.

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