$139 Cheap United flights Phoenix (PHX) to St. Louis (STL)

View $139 flight on Thu, Aug 21, 2025Opens in a new window

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$139 Cheap United flights Phoenix (PHX) to St. Louis (STL)

Prices were available within the past 7 days and start at $139 for one-way flights and $236 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

United
Thu, Oct 9 - Sun, Oct 12
PHX
Phoenix
STL
St. Louis
$236 Roundtrip, found 2 hours ago
$236
Roundtrip
found 2 hours ago
Select United flight, departing Thu, Oct 9 from Phoenix to St. Louis, returning Sun, Oct 12, priced at $236 found 2 hours ago
United
Wed, Aug 6 - Wed, Sep 3
PHX
Phoenix
STL
St. Louis
$272 Roundtrip, found 4 hours ago
$272
Roundtrip
found 4 hours ago
Select United flight, departing Wed, Aug 6 from Phoenix to St. Louis, returning Wed, Sep 3, priced at $272 found 4 hours ago
Flights from Phoenix (PHX) to St. Louis (STL)
Origin airport
Sky Harbor Intl.
Destination airport
Lambert-St. Louis Intl.
Airlines serving
Alaska Airlines, American Airlines, Delta, Frontier Airlines, Southwest Airlines, Spirit Airlines, United
Popular airline
American Airlines
Distance
1259 mi
Average flight time
5 hours 26 mins

Frequently asked questions

How much is a United Airlines flight from Sky Harbor Intl. Airport (PHX) to Lambert-St. Louis Intl. Airport (STL)?
Landing cheap one-way United Airlines flights from PHX to STL from $139 on Expedia couldn't be easier --- just filter by "Price (lowest to highest)." Alternatively, check out our budget-friendly round-trip fares from $236 for your next exciting vacation.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.
What is the cheapest month to fly from PHX to STL with United Airlines?
January is one of the most affordable months to jet away to St. Louis with United Airlines. You could also find great deals on return and one-way fares in February.
What is the cheapest time to book flights from Sky Harbor Intl. Airport (PHX) to Lambert-St. Louis Intl. Airport (STL) with United Airlines?
Start searching one to three months ahead of your travel date to get cheaper fares on United Airlines flights from Sky Harbor Intl. Airport (PHX) to Lambert-St. Louis Intl. Airport (STL). You can save 25% by booking your domestic flight 34 to 86 days in advance versus last-minute reservations made 6 to 12 days out. You could also cut costs by buying your fare on a Sunday, as it's 6% cheaper on average than a Monday, the most expensive day to book.* Get the timing right, and you can enjoy significant savings on domestic flights.*Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC's global airline sales database.
Does United Airlines fly nonstop from Sky Harbor Intl. Airport (PHX) to Lambert-St. Louis Intl. Airport (STL)?
Select our "Nonstop" filter when searching for direct United Airlines flights from PHX to STL. It's also a great way to compare other carriers offering the same nonstop trip.
What is the earliest United Airlines flight from PHX to STL?
Search United Airlines's earliest flights from PHX to STL by using the "Early Morning" and "Morning" filters. Not only will you arrive sooner, early departures are also 20% less likely to be canceled.**Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.
What airports does United Airlines fly into in St. Louis?
Lambert-St. Louis Intl. Airport (STL) is the main St. Louis hub for United Airlines flights from Sky Harbor Intl. Airport (PHX).
Why fly with United Airlines from PHX to STL?
A rewarding loyalty program and the ability to collect points through United Mileage Plus are the start of the reasons to leave from PHX to STL with United Airlines. Plus, when you join our One Key™ program, you can earn OneKeyCash™* alongside any airline loyalty program earnings. It's yours to spend on future bookings.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.
Can I change or cancel my United Airlines flight from Sky Harbor Intl. Airport (PHX) to Lambert-St. Louis Intl. Airport (STL)?
It's usually possible to change or cancel your flight, although there may be additional fees if you made your booking more than 24 hours ago. Need to keep your options open? Use Expedia's "Changes included" and "No cancel fee" filters to find flights that won't charge extra if you have to alter your plans. To modify your itinerary, head to "Trips," select your flight and click on "Manage Booking" for further information.

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*Available to One Key members.