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$643+ Cheap flights from St. Louis (STL) to Porto (OPO)

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 10/10. Fares are subject to change and may not be available on all flights or dates of travel.
STL — OPO
Jul 7 — Jul 141
Mon 7/7
Mon 7/14
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 July 2, 2025.

Round-trip from

$658
(Iberia)

One-way from

$643
(United Airlines)

Popular in

June

Cheapest in

November

Average price

$1,398
From Lambert-St Louis to Porto
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One-way flight from Lambert-St Louis to Porto
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Highest demand for flights based on searches. 24% potential increase in price ($322 potential increase over avg. RT price).
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Cheapest flight prices on average. 3% potential price decrease ($39 potential savings vs. average RT price).
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Average for round-trip flights in July 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 July 2, 2025.

This Iberia 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 Iberia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 10/2811:46 amSTL - OPO
2 stops14h 54mIberia
Sat 11/812:25 pmOPO - STL
2 stops26h 18mIberia
Deal found 6/30$658
This American 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 10/2810:22 amSTL - OPO
2 stops16h 18mAmerican Airlines
Sat 11/88:40 pmOPO - STL
2 stops18h 12mAmerican Airlines
Deal found 7/1$663
This FlightHub 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 10/2811:49 amSTL - OPO
2 stops18h 51mLufthansa
Sat 11/812:40 pmOPO - STL
1 stop31h 15mLufthansa
Deal found 6/30$675
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.
Thu 8/146:00 pmSTL - OPO
2 stops18h 15mDelta
Thu 8/216:30 amOPO - STL
2 stops22h 53mDelta
Deal found 6/30$866
This KLM 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 KLM is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/155:30 pmSTL - OPO
2 stops16h 05mKLM
Fri 8/226:40 amOPO - STL
2 stops22h 34mKLM
Deal found 7/1$897
This Mytrip 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/149:15 amSTL - OPO
3 stops25h 00mMultiple Airlines
Thu 8/217:15 amOPO - STL
2 stops18h 45mMultiple Airlines
Deal found 6/30$919
This Air Canada 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 Air Canada is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/141:30 pmSTL - OPO
2 stops20h 15mAir Canada
Thu 8/2112:10 pmOPO - STL
1 stop13h 50mAir Canada
Deal found 6/30$925
This United Airlines deal was found by Cheapflights users on 6/29. 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.
Tue 9/305:24 pmSTL - OPO
1 stop10h 21mUnited Airlines
Wed 10/156:00 amOPO - STL
2 stops21h 47mUnited Airlines
Deal found 6/29$950

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 July 2, 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

Tue 10/28

11:46 am-7:40 am

2 stops14h 54m

Porto

Sat 11/8

12:25 pm-8:43 am

2 stops26h 18m

$658

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Tue 10/28

10:22 am-7:40 am

2 stops16h 18m

Porto

Sat 11/8

8:40 pm-8:52 am

2 stops18h 12m

$663

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Tue 10/28

11:49 am-11:40 am

2 stops18h 51m

Porto

Sat 11/8

12:40 pm-1:55 pm

1 stop31h 15m

$675

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Thu 8/14

6:00 pm-6:15 pm

2 stops18h 15m

Porto

Thu 8/21

6:30 am-11:23 pm

2 stops22h 53m

$866

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Fri 8/15

5:30 pm-3:35 pm

2 stops16h 05m

Porto

Fri 8/22

6:40 am-11:14 pm

2 stops22h 34m

$897

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Thu 8/14

9:15 am-4:15 pm

3 stops25h 00m

Porto

Thu 8/21

7:15 am-8:00 pm

2 stops18h 45m

$919

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Thu 8/14

1:30 pm-3:45 pm

2 stops20h 15m

Porto

Thu 8/21

12:10 pm-8:00 pm

1 stop13h 50m

$925

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Tue 9/30

5:24 pm-9:45 am

1 stop10h 21m

Porto

Wed 10/15

6:00 am-9:47 pm

2 stops21h 47m

$950

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Fri 10/10

5:24 pm-9:45 am

1 stop10h 21m

$643

St. LouisPorto

STL - OPO

STLOPO

Lambert-St Louis

Thu 9/25

9:46 am-7:35 am

2 stops15h 49m

$657

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/30

Showing 1-10 of 11 results
1
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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 $1,033). 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 July 2, 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 July 2, 2025.
Read reviews from past customers who have flown Delta, KLM, and United Airlines 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
7,983 reviews

Entertainment

7.9

Food

7.3

Boarding

8.2

Overall

8.0

Crew

8.5

Comfort

7.9

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
7,983 reviews
Delta
8.0
Very good
7,983 reviews

Entertainment

7.9

Food

7.3

Boarding

8.2

Overall

8.0

Crew

8.5

Comfort

7.9

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!
KLM
7.8
Good
1,366 reviews
Delta
8.0
Very good
7,983 reviews

Entertainment

7.9

Food

7.3

Boarding

8.2

Overall

8.0

Crew

8.5

Comfort

7.9

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
8,861 reviews
Delta
8.0
Very good
7,983 reviews

Entertainment

7.9

Food

7.3

Boarding

8.2

Overall

8.0

Crew

8.5

Comfort

7.9

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!
American Airlines
7.2
Good
10,000 reviews
Delta
8.0
Very good
7,983 reviews

Entertainment

7.9

Food

7.3

Boarding

8.2

Overall

8.0

Crew

8.5

Comfort

7.9

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!
Air Canada
7.1
Good
9,669 reviews
Delta
8.0
Very good
7,983 reviews

Entertainment

7.9

Food

7.3

Boarding

8.2

Overall

8.0

Crew

8.5

Comfort

7.9

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?

    Iberia, at $658, was found to be the cheapest airline from St. Louis to Porto.Alternate airlines to your destination round-trip include American Airlines and Lufthansa. Users have found that Iberia is 33% cheaper than the other options available to this destination.

  • What are the cheapest airlines to fly from St. Louis to Porto one-way?

    For one-way options, check prices for United Airlines. According to our data, you can fly for as low as $643. Users have also found prices from $657 and $662 on American Airlines and Lufthansa, respectively.

  • 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 $1,033). 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 St. Louis?

Book flights to St. Louis if you plan to visit one of these locations
Aveiro
Coimbra
Matosinhos

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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 July 2, 2025.
AirlineCheapestAverageFlexibilityOn-time
LufthansaCheapest$612Average$1,250FlexibilityNo cancel feeOn-time76%
DeltaCheapest$713Average$963FlexibilityNo cancel feeOn-timeN/A
United AirlinesCheapest$751Average$1,177FlexibilityNo cancel feeOn-time69%

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