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$579+ Cheap flights from St. Louis (STL) to Porto (OPO)

This is the cheapest round-trip flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 11/12. Fares are subject to change and may not be available on all flights or dates of travel.
STL — OPO
Aug 19 — Aug 261
Tue 8/19
Tue 8/26
1 adult, Economy
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Cheap flight deals from St. Louis to Porto

Discover tips and strategies to find the most affordable flight options for your journey from St. Louis (STL) to Porto (OPO). 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 August 14, 2025.

Round-trip from

$579
(United Airlines)

Popular in

June

Cheapest in

November

Average price

$1,117
From Lambert-St Louis to Porto
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Highest demand for flights based on searches. 20% potential increase in price ($275 potential increase over avg. RT price).
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Cheapest flight prices on average. 3% potential price decrease ($34 potential savings vs. average RT price).
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Average for round-trip flights in August 2025
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Find flight deals from St. Louis to Porto

Cheapest flights from St. Louis to Porto
Explore the most affordable flight options available from St. Louis to Porto. Find the lowest fares from popular airlines and budget airlines, with prices last updated on August 14, 2025.

This United deal was found by Cheapflights users on 8/12. 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 is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/1211:49 amSTL - OPO
1 stop15h 41mMultiple Airlines
Wed 11/196:00 amOPO - STL
1 stop13h 55mMultiple Airlines
Deal found 8/12$579
This United Airlines deal was found by Cheapflights users on 8/12. 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 11/1012:31 pmSTL - OPO
2 stops14h 59mUnited Airlines
Wed 11/196:00 amOPO - STL
1 stop13h 55mUnited Airlines
Deal found 8/12$584
This Gurufare deal was found by Cheapflights users on 8/12. 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 Gurufare is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 11/1111:49 amSTL - OPO
1 stop15h 41mLufthansa
Wed 11/196:00 amOPO - STL
1 stop13h 55mLufthansa
Deal found 8/12$591
This United Airlines deal was found by Cheapflights users on 8/12. 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 11/106:30 amSTL - OPO
2 stops21h 00mUnited Airlines
Tue 11/1812:35 pmOPO - STL
2 stops16h 10mUnited Airlines
Deal found 8/12$597
This United Airlines deal was found by Cheapflights users on 8/12. 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.
Sun 11/93:50 pmSTL - OPO
1 stop13h 50mUnited Airlines
Wed 11/196:00 amOPO - STL
1 stop13h 55mUnited Airlines
Deal found 8/12$601
This Ovago deal was found by Cheapflights users on 8/12. 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 Ovago is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/125:40 pmSTL - OPO
2 stops16h 25mBritish Airways
Thu 11/208:20 amOPO - STL
2 stops17h 07mBritish Airways
Deal found 8/12$602
This KAYAK deal was found by Cheapflights users on 8/12. 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 KAYAK is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 11/96:43 pmSTL - OPO
2 stops21h 42mLufthansa
Fri 11/216:00 amOPO - STL
1 stop13h 55mLufthansa
Deal found 8/12$611
This KAYAK deal was found by Cheapflights users on 8/12. 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 KAYAK is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 11/93:50 pmSTL - OPO
1 stop17h 25mLufthansa
Thu 11/206:00 amOPO - STL
2 stops23h 44mLufthansa
Deal found 8/12$616
This KAYAK deal was found by Cheapflights users on 8/12. 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 KAYAK is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 11/106:43 pmSTL - OPO
2 stops21h 42mLufthansa
Thu 11/204:15 pmOPO - STL
1 stop27h 40mLufthansa
Deal found 8/12$630

Cheapflights Fare Finder

 
Customize your flight search to find flights from St. Louis to Porto 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 August 14, 2025.
Use the filters below to find and compare flights from St. Louis to Porto that are best for you.

Fly from

St. Louis

Fly to

Porto

Route

Depart

Return

Price

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Wed 11/12

10:00 am-9:30 am

2 stops17h 30m

Porto

Wed 11/19

6:00 am-1:55 pm

1 stop13h 55m

$579

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Wed 11/12

11:49 am-9:30 am

1 stop15h 41m

Porto

Wed 11/19

6:00 am-1:55 pm

1 stop13h 55m

$579

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Mon 11/10

12:31 pm-9:30 am

2 stops14h 59m

Porto

Wed 11/19

6:00 am-1:55 pm

1 stop13h 55m

$584

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Wed 11/12

10:00 am-9:30 am

2 stops17h 30m

Porto

Fri 11/21

6:00 am-1:55 pm

1 stop13h 55m

$584

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Tue 11/11

11:05 am-9:30 am

2 stops16h 25m

Porto

Wed 11/19

6:00 am-1:55 pm

1 stop13h 55m

$584

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Mon 11/10

12:31 pm-9:30 am

2 stops14h 59m

Porto

Fri 11/21

6:00 am-1:55 pm

1 stop13h 55m

$584

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Tue 11/11

11:05 am-9:30 am

2 stops16h 25m

Porto

Fri 11/21

6:00 am-1:55 pm

1 stop13h 55m

$584

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Wed 11/12

11:49 am-9:30 am

1 stop15h 41m

Porto

Wed 11/19

6:00 am-1:55 pm

1 stop13h 55m

$591

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Thu 9/25

1:26 pm-5:05 pm

2 stops21h 39m

$615

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Fri 10/10

9:35 am-7:35 am

2 stops16h 00m

$657

Flights are sorted by cheapest round-trip flights first.

Deals found on 8/13

Showing 1-10 of 13 results
1
2

Best time to book a flight from St. Louis to Porto

Have a flexible travel schedule? Discover the best time to fly to Porto 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 Porto

What is the cheapest month to book a flight from St. Louis to Porto?

Currently, January is the cheapest month in which you can book a flight from St. Louis to Porto (average of $523). Flying from St. Louis to Porto in June is currently the most expensive (average of $1,029). 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 OPO?

Find hourly flight availability from St. Louis to Porto. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated August 14, 2025.

Unlike in the afternoon, when flights are generally more expensive, you can save up to 36% on flights from St. Louis to Porto by exploring options for tickets at noon.

How much does it cost to fly round-trip from St. Louis to Porto?

Reviews of airlines servicing Porto

Get insights into the airlines that provide service to Porto. 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 Porto. Reviews last updated August 14, 2025.
Read reviews from past customers who have flown Delta, United Airlines, and Lufthansa from St. Louis to Porto. Users can see the overall rating for each airline as well as how each is rated in terms of entertainment options, comfort, food, crew/service, and boarding process.
Delta
8.0
Very good
7,980 reviews

Crew

8.5

Comfort

7.9

Boarding

8.2

Overall

8.0

Entertainment

7.9

Food

7.3

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!
Delta
8.0
Very good
7,980 reviews
Delta
8.0
Very good
7,980 reviews

Crew

8.5

Comfort

7.9

Boarding

8.2

Overall

8.0

Entertainment

7.9

Food

7.3

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!
United Airlines
7.4
Good
8,916 reviews
Delta
8.0
Very good
7,980 reviews

Crew

8.5

Comfort

7.9

Boarding

8.2

Overall

8.0

Entertainment

7.9

Food

7.3

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!
Lufthansa
6.8
Okay
7,317 reviews
Delta
8.0
Very good
7,980 reviews

Crew

8.5

Comfort

7.9

Boarding

8.2

Overall

8.0

Entertainment

7.9

Food

7.3

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!

Related info for your journey

Find useful and relevant information for your journey from St. Louis to Porto. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • What are the cheapest airlines flying from St. Louis to Porto round-trip?

    Lufthansa, at $612, was found to be the cheapest airline from St. Louis to Porto.Alternate airlines to your destination round-trip include Delta and United Airlines. Users have found that Lufthansa is 41% cheaper than the other options available to this destination.

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

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

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

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

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

    Yes. Cheapflights offers flight deals from St. Louis to Porto 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 Porto?

    Currently, January is the cheapest month in which you can book a flight from St. Louis to Porto (average of $523). Flying from St. Louis to Porto in June is currently the most expensive (average of $1,029). 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

Traveling to a place near Porto?

Book flights to Porto if you plan to visit one of these locations
Aveiro
Arcos de Valdevez
Coimbra

Browse thousands of different options on Cheapflights for your next trip

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Alternative routes for St. Louis to Porto

See prices for flight routes from nearby airports that may be better suited for you.
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Top 3 airlines flying from St. Louis to Porto

Discover the top 3 airlines that operate flights from St. Louis to Porto. 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 August 14, 2025.
AirlineCheapestAverageFlexibilityOn-time
LufthansaCheapest$612Average$1,250FlexibilityNo cancel feeOn-time76%
DeltaCheapest$713Average$963FlexibilityNo cancel feeOn-timeN/A
United AirlinesCheapest$751Average$1,220FlexibilityNo cancel feeOn-time69%

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