$129 Cheap Frontier Airlines flights St. Louis (STL) to Islip (ISP)

View $129 flight on Thu, Sep 4, 2025Opens in a new window

  • Plan, book, fly with confidence

  • trending down icon
    Be in the know
    Get alerts if flight prices drop or rise*
  • bex rewards loyalty icon
    Book smarter
    Save up to 30% on select hotels after you book a flight*
  • one key icon
    Earn twice
    Earn your airline miles on top of our OneKeyCash
    Learn about One Key

$129 Cheap Frontier Airlines flights St. Louis (STL) to Islip (ISP)

Prices were available within the past 7 days and start at $129 for one-way flights and $237 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Frontier Airlines
Wed, Aug 6 - Mon, Aug 11
STL
St. Louis
ISP
Islip
$237 Roundtrip, found 6 days ago
$237
Roundtrip
found 6 days ago
Select Frontier Airlines flight, departing Wed, Aug 6 from St. Louis to Islip, returning Mon, Aug 11, priced at $237 found 6 days ago
Frontier Airlines
Thu, Sep 4 - Mon, Sep 8
STL
St. Louis
ISP
Islip
$242 Roundtrip, found 2 days ago
$242
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Thu, Sep 4 from St. Louis to Islip, returning Mon, Sep 8, priced at $242 found 2 days ago
Frontier Airlines
Thu, Sep 11 - Mon, Sep 15
STL
St. Louis
ISP
Islip
$253 Roundtrip, found 4 days ago
$253
Roundtrip
found 4 days ago
Select Frontier Airlines flight, departing Thu, Sep 11 from St. Louis to Islip, returning Mon, Sep 15, priced at $253 found 4 days ago
Frontier Airlines
Mon, Sep 29 - Fri, Oct 3
STL
St. Louis
ISP
Islip
$267 Roundtrip, found 4 days ago
$267
Roundtrip
found 4 days ago
Select Frontier Airlines flight, departing Mon, Sep 29 from St. Louis to Islip, returning Fri, Oct 3, priced at $267 found 4 days ago
Frontier Airlines
Thu, Aug 28 - Mon, Sep 1
STL
St. Louis
ISP
Islip
$268 Roundtrip, found 21 hours ago
$268
Roundtrip
found 21 hours ago
Select Frontier Airlines flight, departing Thu, Aug 28 from St. Louis to Islip, returning Mon, Sep 1, priced at $268 found 21 hours ago
Frontier Airlines
Thu, Aug 28 - Mon, Sep 1
STL
St. Louis
ISP
Islip
$293 Roundtrip, found 21 hours ago
$293
Roundtrip
found 21 hours ago
Select Frontier Airlines flight, departing Thu, Aug 28 from St. Louis to Islip, returning Mon, Sep 1, priced at $293 found 21 hours ago
Flights from St. Louis (STL) to Islip (ISP)
Origin airport
Lambert-St. Louis Intl.
Destination airport
MacArthur
Airlines serving
Frontier Airlines, Southwest Airlines
Popular airline
Southwest Airlines
Distance
926 mi

Frequently asked questions

How much is a Frontier Airlines flight from Lambert-St. Louis Intl. Airport (STL) to MacArthur Airport (ISP)?
Use the "Price (lowest to highest)" filter on Expedia to find cheap Frontier Airlines round-trip flights from $237 from STL to ISP. Affordable one-way fares from $129 are also on offer.**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 STL to ISP with Frontier Airlines?
Frontier Airlines flights to Islip are typically more affordable in the off-peak months of January and February. Whether you need a round-trip or one-way ticket, you could score a better deal then.
What is the cheapest time to book flights from Lambert-St. Louis Intl. Airport (STL) to MacArthur Airport (ISP) with Frontier Airlines?
For cheap Frontier Airlines fares from Lambert-St. Louis Intl. Airport (STL) to MacArthur Airport (ISP), start searching one to three months before your intended departure. Securing domestic flights 34 to 86 days in advance could save you 25% compared to booking just 6 to 12 days ahead. The day you book can also influence the overall cost. Sunday is generally the most affordable, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking your flight on a Sunday.**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 Frontier Airlines fly nonstop from Lambert-St. Louis Intl. Airport (STL) to MacArthur Airport (ISP)?
Enter your dates, click search and tick the "Nonstop" filter on Expedia to find any direct flights from STL to ISP with Frontier Airlines or other airlines.
What is the earliest Frontier Airlines flight from STL to ISP?
To find the earliest departure from STL to ISP with Frontier Airlines, filter your search by "Morning" and "Early Morning." Booking an early flight usually means you'll experience fewer cancellations.**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 Frontier Airlines fly into in Islip?
Frontier Airlines flights from Lambert-St. Louis Intl. Airport (STL) to Islip arrive at MacArthur Airport (ISP). This is the main gateway here.
Why fly with Frontier Airlines from STL to ISP?
A rewarding loyalty program and the ability to rack up points through Frontier Miles are the start of the reasons to fly from STL to ISP with Frontier Airlines. Plus, by joining Expedia's free One Key™ program, you can receive OneKeyCash™* in addition to Frontier Airlines's loyalty program earnings. You can put it toward your future trips.*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 Frontier Airlines flight from Lambert-St. Louis Intl. Airport (STL) to MacArthur Airport (ISP)?
Changes are typically free within 24 hours of making your booking, but your airline may charge a fee after that time. For further details about altering your flights, head to your "Trips," select your flight and click on "Manage Booking." If you want the freedom to adjust your plans without extra charges, check the "No cancel fee" or "Changes included" filter when organizing your trip.

Explore a world of travel with Expedia

*Available to One Key members.