St. Louis

$238+ Cheap flights from Islip, NY to St. Louis (ISP - STL)

This is the cheapest round-trip flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 8/21. Fares are subject to change and may not be available on all flights or dates of travel.
ISP — STL
Jul 30 — Aug 61
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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 July 25, 2025.

Round-trip from

$238
(Frontier)

Popular in

December

Cheapest in

January

Average price

$348
From Islip Long Island to Lambert-St Louis
Highest demand for flights based on searches. 8% potential increase in price ($32 potential increase over avg. RT price).
Cheapest flight prices on average. 2% potential price decrease ($8 potential savings vs. average RT price).
Average for round-trip flights in July 2025

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 July 25, 2025.

This Frontier deal was found by Cheapflights users on 7/23. 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 8/216:05 amISP - STL
1 stop8h 02mFrontier
Sun 8/242:02 pmSTL - ISP
1 stop8h 57mFrontier
Deal found 7/23$238
This Southwest deal was found by Cheapflights users on 7/23. 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 8/153:05 pmISP - STL
1 stop5h 30mSouthwest
Sun 8/178:10 amSTL - ISP
1 stop7h 50mSouthwest
Deal found 7/23$303

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 July 25, 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

Thu 8/21

6:05 am-1:07 pm

1 stop8h 02m

Lambert-St Louis

Sun 8/24

2:02 pm-11:59 pm

1 stop8h 57m

$238

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 8/15

3:05 pm-7:35 pm

1 stop5h 30m

Lambert-St Louis

Sun 8/17

8:10 am-5:00 pm

1 stop7h 50m

$303

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/23

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, August is the cheapest month in which you can book a flight from Islip, New York to St. Louis (average of $311). Flying from Islip, New York 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 July 25, 2025.

When flying from Islip, New York 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 July 25, 2025.
Read reviews from past customers who have flown Southwest and Frontier 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.

Comfort

8.0

Entertainment

7.6

Overall

8.0

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

Comfort

8.0

Entertainment

7.6

Overall

8.0

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

Comfort

8.0

Entertainment

7.6

Overall

8.0

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

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.
  • What are the cheapest airlines flying from Islip, New York to St. Louis round-trip?

    According to our current data, Frontier ($238), and Southwest ($303) offers the cheapest pricing from Islip, New York to St. Louis.

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

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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.

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 July 25, 2025.
AirlineCheapestAverageFlexibilityOn-time
SouthwestCheapest$304Average$386FlexibilityNo cancel feeOn-time63%

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