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$90+ Cheap flights from Islip, NY 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 4/10. Fares are subject to change and may not be available on all flights or dates of travel.
ISP — STL
Apr 18 — Apr 251
Sat 4/18
Sat 4/25
1 adult, Economy
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Cheap 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 March 19, 2026.

This Southwest deal was found by Cheapflights users on 3/15. 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.
Mon 3/305:15 pm
ISP
-
STL
1 stop8h 25m
Southwest
Fri 4/34:45 pm
STL
-
ISP
1 stop6h 10m
Southwest
Deal found 3/15$411
This Southwest deal was found by Cheapflights users on 3/19. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/35:15 pm
ISP
-
STL
1 stop8h 25m
Southwest
Tue 4/71:15 pm
STL
-
ISP
1 stop4h 15m
Southwest
Deal found 3/19$434
This Southwest deal was found by Cheapflights users on 3/15. 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.
Thu 4/25:55 pm
ISP
-
STL
1 stop6h 10m
Southwest
Sun 4/55:50 am
STL
-
ISP
1 stop4h 55m
Southwest
Deal found 3/15$481
This Southwest deal was found by Cheapflights users on 3/15. 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 4/16:10 am
ISP
-
STL
1 stop8h 45m
Southwest
Sun 4/53:50 pm
STL
-
ISP
1 stop6h 05m
Southwest
Deal found 3/15$495
This Southwest deal was found by Cheapflights users on 3/17. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/25:55 pm
ISP
-
STL
1 stop6h 10m
Southwest
Mon 4/67:15 am
STL
-
ISP
1 stop8h 15m
Southwest
Deal found 3/17$578

Find 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 March 19, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$411
(Southwest)

One-way from

$90
(Frontier)

Popular in

November

Cheapest in

August

Average price

$361
Provider with most accurate pricing for Islip Long Island-Lambert-St Louis flight deals.
Search Deals
Provider most trusted by Cheapflights users for Islip Long Island-Lambert-St Louis flights.
Search Deals
From Islip Long Island to Lambert-St Louis
Search Deals
One-way flight from Islip Long Island to Lambert-St Louis
Search Deals
Highest demand for flights based on searches. 11% potential increase in price ($45 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 1% potential price decrease ($6 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in March 2026
Search Deals

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 March 19, 2026.
Use the filters below to find and compare flights from Islip to St. Louis that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 3/30

5:15 pm-12:40 am

1 stop8h 25m

Lambert-St Louis

Fri 4/3

4:45 pm-11:55 pm

1 stop6h 10m

$411

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 4/3

5:15 pm-12:40 am

1 stop8h 25m

Lambert-St Louis

Tue 4/7

5:30 am-1:50 pm

2 stops7h 20m

$439
Quickest round-trip

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 4/2

5:55 pm-11:05 pm

1 stop6h 10m

Lambert-St Louis

Sun 4/5

5:50 am-11:45 am

1 stop4h 55m

$481

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 4/1

6:10 am-1:55 pm

1 stop8h 45m

Lambert-St Louis

Sun 4/5

3:50 pm-10:55 pm

1 stop6h 05m

$495

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 4/2

5:55 pm-11:05 pm

1 stop6h 10m

Lambert-St Louis

Mon 4/6

7:15 am-4:30 pm

1 stop8h 15m

$578
Cheapest one-way

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 4/8

4:10 pm-9:05 pm

1 stop5h 55m

$130

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 4/30

4:30 pm-11:25 pm

1 stop7h 55m

$151

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 4/9

4:30 pm-11:40 pm

2 stops8h 10m

$151

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 4/20

4:07 pm-11:19 pm

1 stop8h 12m

$190

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 4/27

4:07 pm-11:19 pm

1 stop8h 12m

$192

Flights are sorted by cheapest round-trip flights first.

Deals found on 3/17

Showing 1-10 of 14 resultsSorted by cheapest first
1
2
  • Most accurate provider: When it comes to deals on Islip, New York-St. Louis flights, users find the pricing of FlightHub to be most consistent on Cheapflights vs. FlightHub Users can find the same prices on Islip, New York-St. Louis flight deals on Cheapflights vs. FlightHub >95% of the time. Price accuracy is based on data collected from Islip, New York-St. Louis flight searches over the past month and is updated monthly.
  • Most trusted provider: When it comes to deals on Islip, New York-St. Louis flights, Cheapflights users trust FlightHub the most. FlightHub has received a user feedback score of 3 out of 3 stars (3 being the best), meaning they have been trusted the most by Cheapflights users looking for Islip, New York-St. Louis flight deals. Provider user feedback score is based on Cheapflights searches over the past month and is updated monthly.

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, New York to St. Louis?

Currently, March is the cheapest month in which you can book a flight from Islip, New York to St. Louis (average of $109). Flying from Islip, New York to St. Louis in January is currently the most expensive (average of $257). 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.

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, New York to St. Louis?

    Airlines like Southwest fly from Islip, New York to St. Louis in about 8h 25m. The time it takes to get you to your destination can typically vary by up to . Islip, New York and St. Louis are separated by a distance of 926 mi.

  • 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, New York to St. Louis?

    Currently, March is the cheapest month in which you can book a flight from Islip, New York to St. Louis (average of $109). Flying from Islip, New York to St. Louis in January is currently the most expensive (average of $257). 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
Fenton
Swansea
Fairview Heights
Maryland Heights
Collinsville
Eureka
Wentzville
Glencoe
Chesterfield
Alton
Farmington
Festus

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