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$508+ 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 10/27. Fares are subject to change and may not be available on all flights or dates of travel.
STL — OPO
Oct 17 — Oct 241
Fri 10/17
Fri 10/24
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 September 17, 2025.

Round-trip from

$508
(Billigflug)

Popular in

June

Cheapest in

November

Average price

$973
From Lambert-St Louis to Porto
Search Deals
Highest demand for flights based on searches. 17% potential increase in price ($234 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease ($31 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in September 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 September 17, 2025.

This Billigflug deal was found by Cheapflights users on 9/15. 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 Billigflug is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/273:14 pmSTL - OPO
2 stops13h 16mMultiple Airlines
Wed 11/126:00 amOPO - STL
1 stop13h 55mMultiple Airlines
Deal found 9/15$508
This Kiwi.com deal was found by Cheapflights users on 9/16. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/123:50 pmSTL - OPO
1 stop13h 50mLufthansa
Wed 11/196:00 amOPO - STL
1 stop13h 55mLufthansa
Deal found 9/16$522
This United Airlines deal was found by Cheapflights users on 9/15. 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 10/278:20 amSTL - OPO
2 stops20h 10mUnited Airlines
Wed 11/126:00 amOPO - STL
2 stops40h 35mUnited Airlines
Deal found 9/15$532
This United Airlines deal was found by Cheapflights users on 9/16. 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.
Wed 11/1211:05 amSTL - OPO
2 stops16h 25mUnited Airlines
Wed 11/196:00 amOPO - STL
1 stop13h 55mUnited Airlines
Deal found 9/16$534
This United Airlines deal was found by Cheapflights users on 9/16. 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 11/1010:00 amSTL - OPO
2 stops17h 30mUnited Airlines
Wed 11/196:00 amOPO - STL
1 stop13h 55mUnited Airlines
Deal found 9/16$548
This Expedia deal was found by Cheapflights users on 9/15. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/2712:52 pmSTL - OPO
2 stops13h 48mBritish Airways
Wed 11/128:20 amOPO - STL
2 stops18h 03mBritish Airways
Deal found 9/15$551
This United Airlines deal was found by Cheapflights users on 9/16. 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.
Wed 11/123:50 pmSTL - OPO
1 stop13h 50mUnited Airlines
Fri 11/216:00 amOPO - STL
1 stop13h 55mUnited Airlines
Deal found 9/16$552
This United Airlines deal was found by Cheapflights users on 9/16. 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 11/1011:05 amSTL - OPO
2 stops16h 25mUnited Airlines
Tue 11/1812:30 pmOPO - STL
2 stops17h 14mUnited Airlines
Deal found 9/16$556
This Lufthansa deal was found by Cheapflights users on 9/16. 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 Lufthansa is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/123:50 pmSTL - OPO
1 stop17h 35mLufthansa
Thu 11/204:15 pmOPO - STL
1 stop27h 40mLufthansa
Deal found 9/16$572

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 September 17, 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

Mon 10/27

5:58 pm-9:30 am

1 stop10h 32m

Porto

Wed 11/12

6:00 am-1:55 pm

1 stop13h 55m

$527

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Mon 10/27

8:20 am-9:30 am

2 stops20h 10m

Porto

Wed 11/12

6:00 am-4:35 pm

2 stops40h 35m

$532

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-9:54 pm

2 stops21h 54m

$544

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Tue 11/11

1:10 pm-9:30 am

2 stops14h 20m

Porto

Fri 11/21

6:00 am-1:55 pm

1 stop13h 55m

$548

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Mon 11/10

11:05 am-9:30 am

2 stops16h 25m

Porto

Fri 11/21

6:00 am-1:55 pm

1 stop13h 55m

$548

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Wed 11/12

8:25 am-9:30 am

2 stops19h 05m

Porto

Fri 11/21

12:35 pm-10:45 pm

2 stops16h 10m

$556

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Wed 11/12

10:00 am-9:30 am

2 stops17h 30m

Porto

Thu 11/20

12:30 pm-11:44 pm

2 stops17h 14m

$556

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Tue 11/11

12:31 pm-9:30 am

2 stops14h 59m

Porto

Tue 11/18

12:30 pm-1:55 pm

1 stop31h 25m

$567

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Mon 11/10

11:05 am-9:30 am

2 stops16h 25m

Porto

Thu 11/20

12:30 pm-1:55 pm

1 stop31h 25m

$567

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Wed 11/12

12:31 pm-9:30 am

2 stops14h 59m

Porto

Tue 11/18

12:30 pm-1:55 pm

1 stop31h 25m

$567

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/16

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 $1,028). 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 September 17, 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.

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 September 17, 2025.
Read reviews from past customers who have flown 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.
United Airlines
7.4
Good
8,926 reviews

Boarding

7.7

Overall

7.4

Comfort

7.3

Crew

8.1

Entertainment

7.1

Food

6.6

Reviews

1 / 20
10.0
Excellent

Julia,Sep 2025

BUF - DEN

The staff were amazing, from check in to boarding and on the flight. The range of entertainment options were really good as well.
United Airlines
7.4
Good
8,926 reviews
United Airlines
7.4
Good
8,926 reviews

Boarding

7.7

Overall

7.4

Comfort

7.3

Crew

8.1

Entertainment

7.1

Food

6.6

Reviews

1 / 20
10.0
Excellent

Julia,Sep 2025

BUF - DEN

The staff were amazing, from check in to boarding and on the flight. The range of entertainment options were really good as well.
Lufthansa
6.8
Okay
7,409 reviews
United Airlines
7.4
Good
8,926 reviews

Boarding

7.7

Overall

7.4

Comfort

7.3

Crew

8.1

Entertainment

7.1

Food

6.6

Reviews

1 / 20
10.0
Excellent

Julia,Sep 2025

BUF - DEN

The staff were amazing, from check in to boarding and on the flight. The range of entertainment options were really good as well.

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.

  • How long is the flight from St. Louis to Porto?

    There are many flights that can get you from St. Louis to Porto in 20h 10m. Fly via United Airlines to get the fastest option. Airlines will cover a distance of 4154 mi.

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

    Lufthansa, at $601, was found to be the cheapest airline from St. Louis to Porto. An alternate airline flying to your destination would be United Airlines. Users have found that Lufthansa is 44% 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 $1,028). 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

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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 2 airlines flying from St. Louis to Porto

Discover the top 2 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 September 17, 2025.
AirlineCheapestAverageFlexibilityOn-time
LufthansaCheapest$601Average$1,214FlexibilityNo cancel feeOn-time76%
United AirlinesCheapest$751Average$1,227FlexibilityNo cancel feeOn-time69%

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