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$80+ Cheap flights from Islip to St. Louis (ISP - STL)

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 10/18. Fares are subject to change and may not be available on all flights or dates of travel.
ISP — STL
Oct 19 — Oct 261
Sun 10/19
Sun 10/26
1 adult, Economy
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Cheap flight deals from Islip to St. Louis

Discover tips and strategies to find the most affordable flight options for your journey from Islip (ISP) to St. Louis (STL). 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 19, 2025.

Round-trip from

$174
(Cheapflightsfares)

One-way from

$80
(Cheapflightsfares)

Popular in

May

Cheapest in

July

Average price

$310
From Islip Long Island to Lambert-St Louis
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One-way flight from Islip Long Island to Lambert-St Louis
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Highest demand for flights based on searches. 12% potential increase in price ($50 potential increase over avg. RT price).
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Cheapest flight prices on average. 3% potential price decrease ($14 potential savings vs. average RT price).
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Average for round-trip flights in September 2025
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Find flight deals from Islip to St. Louis

Cheapest flights from Islip to St. Louis
Explore the most affordable flight options available from Islip to St. Louis. Find the lowest fares from popular airlines and budget airlines, with prices last updated on September 19, 2025.

This Cheapflightsfares deal was found by Cheapflights users on 9/17. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/1112:00 pmISP - STL
1 stop7h 02mFrontier
Sun 10/121:41 pmSTL - ISP
1 stop6h 11mFrontier
Deal found 9/17$174
This Southwest deal was found by Cheapflights users on 9/18. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/296:00 amISP - STL
1 stop6h 25mSouthwest
Wed 11/56:05 amSTL - ISP
1 stop5h 10mSouthwest
Deal found 9/18$217
This Booking.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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/211:40 amISP - STL
2 stops22h 26mFrontier
Mon 10/69:32 pmSTL - ISP
1 stop22h 10mFrontier
Deal found 9/16$342
This Frontier deal was found by Cheapflights users on 9/17. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/211:40 amISP - STL
2 stops22h 26mFrontier
Sun 10/510:39 amSTL - ISP
2 stops23h 01mFrontier
Deal found 9/17$392
This Frontier deal was found by Cheapflights users on 9/19. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/35:05 pmISP - STL
2 stops17h 01mFrontier
Mon 10/67:55 pmSTL - ISP
2 stops17h 18mFrontier
Deal found 9/19$397
This Frontier deal was found by Cheapflights users on 9/17. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/211:40 amISP - STL
2 stops22h 26mFrontier
Tue 10/77:52 pmSTL - ISP
2 stops17h 21mFrontier
Deal found 9/17$400
This Frontier deal was found by Cheapflights users on 9/19. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/35:05 pmISP - STL
2 stops17h 01mFrontier
Sun 10/57:55 pmSTL - ISP
2 stops16h 52mFrontier
Deal found 9/19$474

Cheapflights Fare Finder

 
Customize your flight search to find flights from Islip to St. Louis 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 19, 2025.
Use the filters below to find and compare flights from Islip to St. Louis that are best for you.

Fly from

Islip

Fly to

St. Louis

Route

Depart

Return

Price

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sat 10/11

12:00 pm-6:02 pm

1 stop7h 02m

Lambert-St Louis

Sun 10/12

1:41 pm-8:52 pm

1 stop6h 11m

$174

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 11/5

3:55 pm-10:00 pm

1 stop7h 05m

Lambert-St Louis

Wed 12/3

6:05 am-12:15 pm

1 stop5h 10m

$217

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 10/29

6:00 am-11:25 am

1 stop6h 25m

Lambert-St Louis

Wed 11/5

6:05 am-12:15 pm

1 stop5h 10m

$217

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 10/2

11:40 am-9:06 am

2 stops22h 26m

Lambert-St Louis

Mon 10/6

9:32 pm-8:42 pm

1 stop22h 10m

$342

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 10/3

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Sun 10/5

10:39 am-10:40 am

2 stops23h 01m

$392

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 10/2

11:40 am-9:06 am

2 stops22h 26m

Lambert-St Louis

Sun 10/5

10:39 am-10:40 am

2 stops23h 01m

$392

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sat 10/4

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Tue 10/7

7:52 pm-2:13 pm

2 stops17h 21m

$397

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 10/3

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Tue 10/7

7:52 pm-2:13 pm

2 stops17h 21m

$397

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 10/3

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Mon 10/6

7:55 pm-2:13 pm

2 stops17h 18m

$397

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sat 10/18

12:38 pm-6:02 pm

1 stop6h 24m

$80

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/18

Showing 1-10 of 16 results
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Best time to book a flight from Islip to St. Louis

Have a flexible travel schedule? Discover the best time to fly to St. Louis from Islip 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 Islip to St. Louis

What is the cheapest month to book a flight from Islip to St. Louis?

Currently, August is the cheapest month in which you can book a flight from Islip to St. Louis (average of $311). Flying from Islip to St. Louis in March is currently the most expensive (average of $356). 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 ISP to STL?

Find hourly flight availability from Islip to St. Louis. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated September 19, 2025.

When flying from Islip to St. Louis, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.

Reviews of airlines servicing St. Louis

Get insights into the airlines that provide service to St. Louis. 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 St. Louis. Reviews last updated September 19, 2025.
Read reviews from past customers who have flown Southwest from Islip to St. Louis. 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.
Southwest
8.0
Very good
4,242 reviews

Food

7.0

Boarding

8.1

Overall

8.0

Entertainment

7.5

Crew

8.6

Comfort

8.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines
Southwest
8.0
Very good
4,242 reviews
Southwest
8.0
Very good
4,242 reviews

Food

7.0

Boarding

8.1

Overall

8.0

Entertainment

7.5

Crew

8.6

Comfort

8.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines

Related info for your journey

Find useful and relevant information for your journey from Islip to St. Louis. 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 Islip to St. Louis?

    There are many flights that can get you from Islip to St. Louis in 7h 02m. Fly via Frontier or Southwest to get the fastest option. Airlines will cover a distance of 926 mi. This flight may include one or multiple stops.

  • What is the cheapest airline to fly from Islip to St. Louis round-trip?

    Currently priced at $304, Southwest will fly you from Islip to St. Louis and back. In addition to Southwest, many other airlines offer competitively priced options for your trip. Southwest is priced at 17% lower than the current average price of a flight leaving 3 months from now.

  • Can I find deals for flights from Islip to St. Louis that include hotel bookings?

    Yes. In addition to deals on Islip to St. Louis flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Islip to St. Louis?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Islip to St. Louis.

  • Can I find deals for business class flights from Islip to St. Louis?

    Yes. Cheapflights offers flight deals from Islip to St. Louis 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 Islip to St. Louis?

    Currently, August is the cheapest month in which you can book a flight from Islip to St. Louis (average of $311). Flying from Islip to St. Louis in March is currently the most expensive (average of $356). 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
Edwardsville
O'Fallon
Fairview Heights
Maryland Heights
Collinsville
Eureka
Glencoe
St. Peters
Chesterfield
Alton
Farmington
Festus

Browse thousands of different options on Cheapflights for your next trip

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Alternative routes for Islip to St. Louis

See prices for flight routes from nearby airports that may be better suited for you.
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Top airline flying from Islip to St. Louis

Discover the top airline that operate flights from Islip to St. Louis. 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 19, 2025.
AirlineCheapestAverageFlexibilityOn-time
SouthwestCheapest$304Average$391FlexibilityNo cancel feeOn-time63%

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