Dulles Intl

$111+ Cheap flights from St. Louis (STL) to Dulles Intl (IAD)

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 7/31. Fares are subject to change and may not be available on all flights or dates of travel.
STL — IAD
Jul 7 — Jul 141
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Cheapflights Tip: The best prices from Lambert-St Louis to Washington, D.C. Dulles Intl are usually found in August or January, booked 75 days in advance, depart on a Friday or Tuesday and return on a Wednesday

Cheap flight deals from St. Louis to Dulles Intl

Discover tips and strategies to find the most affordable flight options for your journey from St. Louis (STL) to Dulles Intl (IAD). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated July 2, 2025.

Round-trip from

$209
(Priceline)

One-way from

$111
(Frontier)

Popular in

July

Cheapest in

August

Average price

$545

Good round-trip deal

$924 or less

Good one-way deal

$219 or less
From Lambert-St Louis to Washington, D.C. Dulles Intl
One-way flight from Lambert-St Louis to Washington, D.C. Dulles Intl
Highest demand for flights based on searches. 8% potential increase in price ($32 potential increase over avg. RT price).
Cheapest flight prices on average. 4% potential price decrease ($16 potential savings vs. average RT price).
Average for round-trip flights in July 2025
Price to beat on a round-trip flight from Lambert-St Louis to Washington, D.C. Dulles Intl.
Price to beat on a one-way flight from Lambert-St Louis to Washington, D.C. Dulles Intl.

Find flight deals from St. Louis to Dulles Intl

Cheapest flights from St. Louis to Dulles Intl
Explore the most affordable flight options available from St. Louis to Dulles Intl. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 2, 2025.

This Priceline deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 7/312:36 pmSTL - IAD
1 stop8h 36mFrontier
Sun 8/311:02 amIAD - STL
1 stop8h 57mFrontier
Deal found 7/1$209
This Delta deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/246:00 pmSTL - IAD
1 stop4h 06mDelta
Mon 9/2912:08 pmIAD - STL
1 stop5h 40mDelta
Deal found 6/30$217
This United Airlines deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 8/185:30 pmSTL - IAD
1 stop6h 00mUnited Airlines
Sun 8/248:40 amIAD - STL
Nonstop2h 22mUnited Airlines
Deal found 7/1$223
This American Airlines deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/305:27 amSTL - IAD
1 stop6h 21mAmerican Airlines
Mon 9/16:34 amIAD - STL
1 stop6h 28mAmerican Airlines
Deal found 6/30$251
This Southwest deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/276:20 amSTL - IAD
1 stop8h 55mSouthwest
Wed 9/35:45 amIAD - STL
2 stops13h 05mSouthwest
Deal found 6/30$263

Cheapflights Fare Finder

Customize your flight search to find flights from St. Louis to Dulles Intl that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated July 2, 2025.
Use the filters below to find and compare flights from St. Louis to Washington, D.C. Dulles Intl Airport that are best for you.

Fly from

St. Louis

Fly to

Dulles Intl

Route

Depart

Return

Price

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Thu 7/31

2:36 pm-12:12 am

1 stop8h 36m

Washington, D.C. Dulles Intl

Sun 8/3

11:02 am-6:59 pm

1 stop8h 57m

$209

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Wed 9/24

6:00 pm-11:06 pm

1 stop4h 06m

Washington, D.C. Dulles Intl

Mon 9/29

12:08 pm-4:48 pm

1 stop5h 40m

$217

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Mon 8/18

5:30 pm-12:30 am

1 stop6h 00m

Washington, D.C. Dulles Intl

Sun 8/24

8:40 am-10:02 am

Nonstop2h 22m

$223

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Sat 8/30

5:27 am-12:48 pm

1 stop6h 21m

Washington, D.C. Dulles Intl

Mon 9/1

6:34 am-12:02 pm

1 stop6h 28m

$251

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Wed 8/27

6:20 am-4:15 pm

1 stop8h 55m

Washington, D.C. Dulles Intl

Wed 9/3

5:45 am-5:50 pm

2 stops13h 05m

$263

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Thu 7/31

8:44 pm-10:07 am

1 stop12h 23m

$111

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Thu 8/7

8:15 am-11:23 am

Nonstop2h 08m

$112

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Thu 8/21

9:50 am-6:15 pm

2 stops7h 25m

$114

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Sat 9/6

6:40 am-11:32 am

1 stop3h 52m

$123

St. LouisWashington, D.C.

STL - IAD

STLIAD

Lambert-St Louis

Thu 9/11

5:27 am-11:34 am

1 stop5h 07m

$126

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/30

Showing 1-10 of 11 results
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The best insider tips for St. Louis to Washington, D.C. Dulles Intl Airport flights

Snippets provided in this section are AI-generated based on a summarization of Cheapflights-commissioned articles. The articles are presented as-is, for general informational purposes only, and may not be up-to-date. The opinions contained in the articles are original to the author and reflect their authentic experience, which may vary significantly from the experience of others.
Cheapflights partnered with top experts to bring you the best recommendations for your St. Louis to Washington, D.C. Dulles Intl Airport trip
Airports
STL

Expect security screening at STL to take 5-10 minutes during off-peak times. Check real-time wait times online before heading to the airport.

Read more about STLby Taryn White
IAD

The Washington Metro Silver Line reaches IAD in under 40 minutes, offering a cheap and convenient way to get to the airport.

Read more about IADby Ramsey Qubein
Our travel experts
Taryn White

Taryn White

Expert on STL

Taryn White

Taryn White

Taryn White is a freelance travel writer, digital creator, and travel advisor who has visited nearly 100 countries and all 50 states. She’s familiar with many airports and enjoys beach hopping, boutique hotels, spa experiences, and exploring local culture. Her work has appeared in Travel + Leisure, Condé Nast Traveler, National Geographic, Smithsonian Magazine, AFAR, and more.

Read more
Ramsey Qubein

Ramsey Qubein

Expert on IAD

Ramsey Qubein

Ramsey Qubein

An avid traveler and aviation expert who has visited 173 countries, all 50 states and seven continents, Ramsey Qubein flies nearly 400,000 miles a year. As a North Carolina-based freelance journalist for publications including Conde Nast Traveler, Forbes, USA Today and Bloomberg among others, he explores the latest trends in aviation, hospitality, cruises and business.

Read more

Best time to book a flight from St. Louis to Dulles Intl

Have a flexible travel schedule? Discover the best time to fly to Dulles Intl from St. Louis with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from St. Louis to Washington, D.C. Dulles Intl Airport

How far ahead should I book a flight from St. Louis to Washington, D.C. Dulles Intl Airport?

Use this chart to determine the optimal time to book a round-trip flight from St. Louis to Dulles Intl. Price data was last updated on June 27, 2025.

The best time to book flights from St. Louis to Washington, D.C. Dulles Intl Airport is 75 days before your desired departure date. The cost of your flight will likely increase significantly if you book two weeks in advance of your flight.

What is the cheapest month to book a flight from St. Louis to Washington, D.C. Dulles Intl Airport?

Currently, August is the cheapest month in which you can book a flight from St. Louis to Washington, D.C. Dulles Intl Airport (average of $309). Flying from St. Louis to Washington, D.C. Dulles Intl Airport in July is currently the most expensive (average of $345). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from STL to IAD?

Find hourly flight availability from St. Louis to Dulles Intl. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated July 2, 2025.

It’s optimal to fly from St. Louis to Washington, D.C. Dulles Intl Airport in the evening. By choosing this option you can save up to 79% on the cost of your flight, compared to a flight at noon.

Weekly flight availability from St. Louis to Washington, D.C. Dulles Intl Airport

Explore weekly flight availability from St. Louis to Dulles Intl. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated July 2, 2025.

The most flights from STL to IAD are scheduled on a Monday (7 on average). You will have fewer flight options on Wednesday, which is when the least amount of flights are scheduled (6 on average).

Reviews of airlines servicing Dulles Intl

Get insights into the airlines that provide service to Dulles Intl. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Dulles Intl. Reviews last updated July 2, 2025.
Peruse reviews from past customers who have flown with Southwest, Delta, and United Airlines from St. Louis to Washington, D.C. Dulles Intl Airport to help guide your decision. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.

Entertainment

7.6

Food

7.0

Boarding

8.2

Overall

8.0

Crew

8.6

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

Entertainment

7.6

Food

7.0

Boarding

8.2

Overall

8.0

Crew

8.6

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.
8.0
Very good

Entertainment

7.6

Food

7.0

Boarding

8.2

Overall

8.0

Crew

8.6

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

Entertainment

7.6

Food

7.0

Boarding

8.2

Overall

8.0

Crew

8.6

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

Entertainment

7.6

Food

7.0

Boarding

8.2

Overall

8.0

Crew

8.6

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

Entertainment

7.6

Food

7.0

Boarding

8.2

Overall

8.0

Crew

8.6

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

Related info for your journey

Find useful and relevant information for your journey from St. Louis to Dulles Intl. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.
  • What airport do you fly from for flights from St. Louis to Washington, D.C. Dulles Intl?

    Most people fly from Lambert-St Louis (STL) if they book a flight from St. Louis to Washington, D.C. Dulles Intl. On average, Lambert-St Louis has 6 outbound flights to Washington, D.C. Dulles Intl per day from 3 airlines. Lambert-St Louis is conveniently located just 12.7 mi from St. Louis’s city center.

  • What are the cheapest airlines flying from St. Louis to Washington, D.C. Dulles Intl Airport round-trip?

    Currently priced at $209, Frontier will fly you from St. Louis to Washington, D.C. Dulles Intl Airport and back. In addition to Frontier, many other airlines offer competitively priced options for your trip. Search Cheapflights for deals from Delta and United Airlines - these airlines can fly you to your destination from $217 and $223, respectively. Frontier is 44% cheaper than the average price of flights available within the next 90 days to this destination.

  • What are the cheapest airlines to fly from St. Louis to Washington, D.C. Dulles Intl Airport one-way?

    To fly one-way, consider booking your trip with Frontier, which is currently one of the cheapest options available, starting at $111. United Airlines flights start at $112 while deals on Southwest start at $114 one-way.

  • What are the most reliable airlines from St. Louis to Washington, D.C. Dulles Intl Airport?

    No one likes to see their flight delayed. When booking a flight from St. Louis to Washington, D.C. Dulles Intl Airport consider choosing Avianca (73%), Copa Airlines (73%) or GoJet (70%) as they are the most reliable in getting you off to your destination on time.

  • What are the cheapest flights from St. Louis to Washington, D.C. Dulles Intl Airport?

    On average you can expect to pay $1,331 for a flight from St. Louis to Washington, D.C. Dulles Intl Airport. The cheapest flight overall is $149 while the most popular route, (Lambert-St Louis - Washington, D.C. Dulles Intl) is currently priced at $183.

  • Can I find deals for flights from St. Louis to Dulles Intl that include hotel bookings?

    Yes. In addition to deals on St. Louis to Dulles Intl flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from St. Louis to Dulles Intl?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from St. Louis to Dulles Intl.

  • Can I find deals for business class flights from St. Louis to Dulles Intl?

    Yes. Cheapflights offers flight deals from St. Louis to Dulles Intl by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from St. Louis to Washington, D.C. Dulles Intl Airport?

    Currently, August is the cheapest month in which you can book a flight from St. Louis to Washington, D.C. Dulles Intl Airport (average of $309). Flying from St. Louis to Washington, D.C. Dulles Intl Airport in July is currently the most expensive (average of $345). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

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Top 3 airlines flying from St. Louis to Dulles Intl

Discover the top 3 airlines that operate flights from St. Louis to Dulles Intl. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated July 2, 2025.
AirlineCheapestAverageFlexibilityOn-time
American AirlinesCheapest$129Average$408FlexibilityNo cancel feeOn-time71%
DeltaCheapest$191Average$263FlexibilityNo cancel feeOn-timeN/A
United AirlinesCheapest$209Average$436FlexibilityNo cancel feeOn-time69%

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