STL - OPO

$366 Find Cheap Flights from St. Louis to Porto

This is the cheapest one-way flight price found by a KAYAK user in the last 72 hours by searching for a flight from St. Louis to Porto departing on 12/9. Fares are subject to change and may not be available on all flights or dates of travel. Click the price to replicate the search for this deal.
1 adult
1 adult, Economy

KAYAK searches hundreds of travel sites at once for deals on flights to Porto

 
These are the airlines KAYAK users have selected most often from within our search results in flight searches from St. Louis to Porto, as well as popular online travel agencies
These are the airlines KAYAK users have selected most often from within our search results in flight searches from St. Louis to Porto, as well as popular online travel agencies
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Flight Deals

Cheap Flights from St. Louis to Porto (STL-OPO)

 
Here are some of the best deals found on KAYAK recently from the most popular airlines for round-trip flights from St. Louis to Porto that are departing in the next months. While these flights were available on KAYAK in the last 72 hours, prices and availability are subject to change and deals may expire.
Discover the best prices for you by selecting your travel dates on KAYAK.

Recent round-trip flight deals from St. Louis to Porto

Mon, Oct 27 - Wed, Nov 12
Multiple Airlines Logo
3:14 pm - 9:30 amSTL-OPO
13h 16m2 stops
Multiple Airlines Logo
6:00 am - 1:55 pmOPO-STL
13h 55m1 stop
$508Multiple Airlines
Find Deal
Wed, Nov 12 - Wed, Nov 19
Lufthansa Logo
3:50 pm - 11:40 amSTL-OPO
13h 50m1 stop
Lufthansa Logo
6:00 am - 1:55 pmOPO-STL
13h 55m1 stop
$522Lufthansa
Find Deal
Mon, Oct 27 - Wed, Nov 12
United Airlines Logo
8:20 am - 9:30 amSTL-OPO
20h 10m2 stops
United Airlines Logo
6:00 am - 4:35 pmOPO-STL
40h 35m2 stops
$532United Airlines
Find Deal
Wed, Nov 12 - Wed, Nov 19
United Airlines Logo
11:05 am - 9:30 amSTL-OPO
16h 25m2 stops
United Airlines Logo
6:00 am - 1:55 pmOPO-STL
13h 55m1 stop
$534United Airlines
Find Deal
Mon, Oct 27 - Wed, Nov 12
British Airways Logo
12:52 pm - 7:40 amSTL-OPO
13h 48m2 stops
British Airways Logo
8:20 am - 8:23 pmOPO-STL
18h 03m2 stops
$551British Airways
Find Deal
Sun, Nov 9 - Tue, Nov 18
Delta Logo
9:04 am - 10:30 amSTL-OPO
19h 26m2 stops
Delta Logo
11:10 am - 8:24 amOPO-STL
27h 14m2 stops
$577Delta
Find Deal
Sun, Nov 9 - Fri, Nov 21
Delta Logo
9:04 am - 10:30 amSTL-OPO
19h 26m2 stops
Delta Logo
11:20 am - 9:46 amOPO-STL
28h 26m2 stops
$583Delta
Find Deal
Thu, Oct 30 - Thu, Nov 6
British Airways Logo
12:51 pm - 7:40 amSTL-OPO
13h 49m2 stops
British Airways Logo
8:20 am - 11:56 pmOPO-STL
21h 36m2 stops
$608British Airways
Find Deal
Mon, Nov 10 - Sat, Nov 22
Air Canada Logo
4:05 pm - 11:15 amSTL-OPO
37h 10m2 stops
Air Canada Logo
6:00 am - 3:29 pmOPO-STL
39h 29m2 stops
$640Air Canada
Find Deal
Tue, Nov 11 - Sat, Nov 22
Air Canada Logo
4:05 pm - 11:40 amSTL-OPO
37h 35m2 stops
Air Canada Logo
6:00 am - 3:29 pmOPO-STL
39h 29m2 stops
$649Air Canada
Find Deal

Everything you should know

Top airlines
Lufthansa
Cheapest • from $522 (round-trip)
United Airlines
Best reviews • 7.4 score
Airline reviews
Airline reviews
+1
+1
Airline reviews
Airline reviews
+1
When to travel
November
Cheapest • 41% price drop
April
Most popular
Good to know
Good to know
+1
+1
Good to know
Good to know
+1
Cheapest round-trip
$508
Overall average: $896
Multiple Airlines
Mon 10/27Wed 11/12
STL - OPO • 2 stops
Cheapest one-way
$366
Multiple Airlines
Tue 12/9
STL - OPO • 3 stops
Start a new search
KAYAK searches 100s of sites at once to find you the best travel deals.
We hope you love your trip to Porto!
Booking Insights

KAYAK's insights & trends for St. Louis to Porto flights

Get data-powered insights and trends into flights from St. Louis to Porto to help you find the cheapest flights, the best time to fly and much more.

What is the cheapest month to fly from St. Louis to Porto?

To calculate monthly average prices, KAYAK takes all prices for each month over the last year for round-trip flights from St. Louis to Porto, removes the top 0.1% to account for outliers, and then takes the median of all values for each month.

The cheapest month for flights from St. Louis to Porto is November, where tickets cost $636 (return) on average. On the other hand, the most expensive months are June and July, where the average cost of round-trip tickets is $1,410 and $1,398 respectively.

Good to know

Low seasonJanuary
Cheapest flight$366
Best time to beat the crowds but there is an average 12% increase in price.
Most popular time to fly with an average 15% increase in price.
Flight from St. Louis to Porto

When to book flights from St. Louis to Porto

Are your dates flexible? Find out the best times to travel from St. Louis to Porto based on our flight data from the last year. Discover the cheapest month and even day to fly.
Estimated round-trip price
KAYAK looks at all historical flight data for each date to provide a predicted price for one-way trips or round-trips with a duration up to 40 days. While we try to provide actual minimum prices for each date, some prices are predictions and actual prices may differ.

FAQs for booking flights from St. Louis to Porto

  • What is the cheapest flight from St. Louis to Porto?

    In the last 3 days, the lowest price for a flight from St. Louis to Porto was $366 for a one-way ticket and $508 for a round-trip.

  • Do I need a passport to fly between St. Louis and Porto?

    Yes, you’ll need a passport to travel to Porto from St. Louis.

  • Which airports will I be using when flying from St. Louis to Porto?

    St. Louis and Porto are both served by 1 main airport. You will leave St. Louis from Lambert-St Louis and will be arriving at Porto.

  • Which aircraft models fly most regularly from St. Louis to Porto?

    We unfortunately don’t have that data for this specific route.

  • Which airline alliances offer flights from St. Louis to Porto?

    Star Alliance, oneworld, and SkyTeam are the airline alliances operating flights between St. Louis and Porto, with Star Alliance being the most commonly used for this route.

  • Which is the best airline for flights from St. Louis to Porto, United Airlines or Lufthansa?

    The two airlines most popular with KAYAK users for flights from St. Louis to Porto are United Airlines and Lufthansa. With an average price for the route of $1,227 and an overall rating of 7.4, United Airlines is the most popular choice. Lufthansa is also a great choice for the route, with an average price of $1,214 and an overall rating of 6.8.

  • How does KAYAK find such low prices on flights from St. Louis to Porto?

    KAYAK is a travel search engine. That means we look across the web to find the best prices we can find for our users. With over 2 billion flight queries processed yearly, we are able to display a variety of prices and options on flights from St. Louis to Porto.

  • How does KAYAK's flight Price Forecast tool help me choose the right time to buy my flight ticket from St. Louis to Porto?

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight to Porto from St. Louis is likely to change within 7 days, so travelers know whether to wait or book now.

  • What is the Hacker Fare option on flights from St. Louis to Porto?

    Hacker Fares allow you to combine one-way tickets in order to save you money over a traditional round-trip ticket. You could then fly to Porto with an airline and back to St. Louis with another airline. Booking your flights between St. Louis and OPO can sometimes prove cheaper using this method.

  • What is KAYAK's "flexible dates" feature and why should I care when looking for a flight from St. Louis to Porto?

    Sometimes travel dates aren't set in stone. If your preferred travel dates have some wiggle room, flexible dates will show you all the options when flying to Porto from St. Louis up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

Reviews of the top airlines flying from St. Louis to Porto

 
See real verified KAYAK customer reviews for airlines flying from St. Louis to Porto. Airline scores are aggregated from all reviews left by passengers on KAYAK after flying with an airline. KAYAK doesn’t show reviews that are older than 5 years. Learn how KAYAK collects reviews.
Need help choosing which airline to fly with from St. Louis to Porto? KAYAK airline reviews give an overall score for each airline based on loads of factors, including comfort, boarding, in-flight entertainment and more, to make your decision easier. See airline scores according to verified KAYAK customer reviews.
7.4
United AirlinesOverall score based on 8924 reviews
7.7Boarding
6.6Food
7.3Comfort
8.1Crew
7.1Entertainment
Airline reviews

Terrible. They wouldn't allow me on my flight on the 14th..

2.0 MediocreJulian, Sep 2025DEN - DRO
Read more United Airlines reviews

Terrible. They wouldn't allow me on my flight on the 14th..

We had to deboard 2 times due to maintenance issues. They changed the plane, and then we got deviated to LAX due to maibtenance issues on the other plane, had to sleep at LAX and los a full day.

Everything was good, except the seats in economy were so close together, you could barely get out when the seat in front of your was reclined. If the airlines keep jamming in more and more seats, it will become intolerable. I will look for another airline that considers customer comfort and does not keep adding more rows of seats for more profit.

The newer screen was super cool and had the option to watch many different shows or movies. Crew was polite and helpful. However again, many children screaming bloody murder and kicking my seat, and parents doing nothing about it as usual.

Flight was good and crew was super polite. However, there were around 5 kids screaming the WHOLE 2 hours. I understand kids have to come but parents need to do something to control their children. They make the experience terrible, especially after finishing 16 hour shifts at the hospital I needed some sleep, which I did not get.

IAD with the archaic people movers is just a place to be avoided.

Great service on board. Boarding a bit slow due to process. Food was pretty average.

Tastless food and too obvious lack of enthusiasm for service in the economy vesus business class

All of the United employees I interacted with were professional and courteous. The aircraft was clean, the food on the flight was good. No complaints here.

I had no checked baggage but was required to hand over carry on baggage at the door of the plane. There was a lot of overboard space in the plane and I was one of the last ones. I ran to get my carry on but it was gone. I was given back at the plane door in Toronto, so the wait was not as long as it would have been at the carousel.

I liked Quiet people around me. Crew could have helped people with overhead luggage so they aren't moving other peoples bags around and causing problems for people that had there bags there first

The flight and crew were good. The customer experience on the ground could have been better. We had to reschedule our flight because of a delay on the previous flight. The attendants working the desk in Washington DC were not helpful. They told us to scan a QR code and that would get us rebooked. Why couldn't two people standing at their computers do this? We had to chat with someone to get everything figured out. It was extremely confusing.

The plane was delayed by two hours in Chicago which led to us missing the next flight. Lufthansa rebooked the flight and booked us a hotel for the night in Frankfurt. The level of customer service and getting us taken care of was superb. The flight crew and the service on the ground was superb.

It was a short flight, everything was good with it.

Flight was delayed over one hour and I had to pay to select my seat, even though my booking supposedly had free selection (I paid extra for this at time of booking)

Stop charging for alcohol overseas flights and start taking cash again not everyone wants to pay with card if the person is bigger give him seat on the outside seats not the middle in between the people is common sense and mainly if you fly for Lufthansa provides the sam service and experience...

good entertainment package but rather small seats for business class

The male attendant has zero personality. It seemed like he was over worked or hated his job, not once did he smile or made any contact with the people on the plane. Strictly business and call it a day!

Booked Economy but it translated to economy light for Lufthansa so now we are stuck paying an extra $75 per person both ways for our checked bags. If I had known that, I would have never booked these tickets because it came out to be more than other options. The booking in the kayak side clearly says Economy and has a link to the inormation for Lufthansa which states Economy included a checked bag. Super annoyed about that.

The flight from Dulles to Munich was just okay. The seats were comfortable and extra foot room was noticeable in comfort plus. Disappointed in the booking in so much I requested an aisle seat and then was assigned a middle seat. The food was inedible. Movie choices were moderate. I usually fly Delta, but this WA flight was cheaper. Next time, I'll happily pay the extra to fly Delta.

Everything you need to know for your flight from St. Louis to Porto

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