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

Our cheapest airline available from St. Louis to Islip, New York is Frontier. Our recent data shows that you can find tickets from as low as $333 on this airline. An additional option worth looking into is Southwest, starting at $372. Frontier is priced at 12% lower than the current average price of a flight leaving 3 months from now.

What is the cheapest day to fly from St. Louis to Islip, New York?

Travelers seeking maximum savings on their St. Louis to Islip, New York flight should consider departing on Saturday evenings when fares are most often at their lowest. Thursday mornings flights should be avoided if possible as fares are typically the most expensive at this time.

In terms of precipitation, rainfall in Islip, New York ranges from 3.3 - 4.4 inches per month. March is typically the wettest month, when rainfall can reach 4.4 in. February is typically the driest time to visit Islip, New York when rainfall is around 3.3 in.

If weather is an important factor for your trip to Islip, New York, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 73.4 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 30.2 F).

What is the cheapest day to fly round-trip from St. Louis to Islip, New York?

Departing on a Friday is a good option for securing a great price. You can expect to save up to 166% when planning your travel around this day of the week.

How far in advance should I book a flight from St. Louis to Islip, New York?

When searching for a good deal, it’s best to be prepared for potential fluctuations in price. We recommend booking at least 45 days in advance, which can save you up to 66% on flights from St. Louis to Islip, New York compared to booking the week you need them. Waiting 45 days out may not be for everyone, so we have options available for flights within the next two weeks, with the lowest price starting at $367. For sooner than that we have options available in the next 3 days from $373.

What is the cheapest month to fly from St. Louis to Islip, New York?

Due to multiple factors, expect to potentially pay more when booking in November. For low rates, April can be a great choice for travel to Islip, New York. Flights to Islip, New York from St. Louis in April are about $309 on average during April, but can be found for as low as $89.

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

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

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

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

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

Yes. Cheapflights offers flight deals from St. Louis to Islip by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

$137+ Flights from St. Louis to Islip, NY

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Cheap flight deals from St. Louis to Islip

Round-trip from	$333 (Gotogate)
One-way from	$137 (Trip.com)
Popular in	March
Cheapest in	April
Average price	$319

From Lambert-St Louis to Islip Long Island

Search Deals

One-way flight from Lambert-St Louis to Islip Long Island

Search Deals

Highest demand for flights based on searches. 2% potential increase in price ($10 potential increase over avg. RT price).

Search Deals

Cheapest flight prices on average. 4% potential price decrease ($15 potential savings vs. average RT price).

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Average for round-trip flights in July 2025

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Find flight deals from St. Louis to Islip

Cheapest flights from St. Louis to Islip
Explore the most affordable flight options available from St. Louis to Islip. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 3, 2025.

Sun 8/35:40 pmSTL - ISP

1 stop25h 12mFrontier

Sat 8/98:37 pmISP - STL

1 stop28h 10mFrontier

Deal found 7/1

$333

Sun 8/35:20 pmSTL - ISP

1 stop5h 35mSouthwest

Sat 8/95:40 amISP - STL

2 stops9h 35mSouthwest

Deal found 7/1

$372

Best flights from St. Louis to Islip
Discover carefully curated flight deals from St. Louis to Islip that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated July 3, 2025.

Sun 8/35:40 pmSTL - ISP

1 stop25h 12mFrontier

Sat 8/98:37 pmISP - STL

1 stop28h 10mFrontier

Deal found 7/1

$333

Sun 8/35:20 pmSTL - ISP

1 stop5h 35mSouthwest

Sat 8/95:40 amISP - STL

2 stops9h 35mSouthwest

Deal found 7/1

$372

Last-minute flights from St. Louis to Islip
Discover last-minute flight deals from St. Louis to Islip. Data last updated July 3, 2025 and is based on user searches.

Tue 7/85:40 pmSTL - ISP

1 stop25h 12mFrontier

Fri 7/118:37 pmISP - STL

1 stop28h 10mFrontier

Deal found 7/2

$358

Tue 7/85:25 amSTL - ISP

2 stops5h 35mSouthwest

Fri 7/115:05 amISP - STL

1 stop7h 00mSouthwest

Deal found 7/2

$677

Sun 8/35:40 pmSTL - ISP

1 stop25h 12mFrontier

Sat 8/98:37 pmISP - STL

1 stop28h 10mFrontier

Deal found 7/1

$333

Sun 8/35:20 pmSTL - ISP

1 stop5h 35mSouthwest

Sat 8/95:40 amISP - STL

2 stops9h 35mSouthwest

Deal found 7/1

$372

One-way flights from St. Louis to Islip
Search for one-way flight options from St. Louis to Islip. Find affordable one-way fares based on user searches. Data last updated July 3, 2025.

Sun 9/72:02 pmSTL - ISP

1 stop19h 38mFrontier

Deal found 7/1

$137

Sun 9/72:30 pmSTL - ISP

3 stops22h 15mMultiple Airlines

Deal found 7/1

$238

Cheapflights Fare Finder

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

Fly from

Fly to

Route

Depart

Return

Price

St. LouisIslip

STL - ISP

STLISP

Lambert-St Louis

Sun 8/3

5:40 pm-7:52 pm

1 stop25h 12m

Islip Long Island

Sat 8/9

8:37 pm-11:47 pm

1 stop28h 10m

$333

St. LouisIslip

STL - ISP

STLISP

Lambert-St Louis

Sun 8/3

5:20 pm-11:55 pm

1 stop5h 35m

Islip Long Island

Sat 8/9

5:40 am-2:15 pm

2 stops9h 35m

$372

St. LouisIslip

STL - ISP

STLISP

Lambert-St Louis

Sun 9/7

2:02 pm-10:40 am

1 stop19h 38m

$137

St. LouisIslip

STL - ISP

STLISP

Lambert-St Louis

Sun 9/7

2:30 pm-1:45 pm

3 stops22h 15m

$238

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/1

Best time to book a flight from St. Louis to Islip

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

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

Currently, January is the cheapest month in which you can book a flight from St. Louis to Islip, New York (average of $108). Flying from St. Louis to Islip, New York in November is currently the most expensive (average of $213). 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 STL to ISP?

A simple way to save on the total cost of your ticket is to fly from St. Louis to Islip, New York at noon. If you’re flexible enough to do this you can expect to save up to 60% on your trip compared to booking a flight in the morning.

Reviews of airlines servicing Islip

Peruse reviews from past customers who have flown with Southwest and Frontier from St. Louis to Islip to help guide your decision. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.

Southwest

8.0

Very good

4,266 reviews

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.

Southwest

8.0

Very good

4,266 reviews

Southwest

8.0

Very good

4,266 reviews

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.

Frontier

5.9

Fair

3,286 reviews

Southwest

8.0

Very good

4,266 reviews

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

What are the cheapest airlines flying from St. Louis to Islip, New York round-trip?
Our cheapest airline available from St. Louis to Islip, New York is Frontier. Our recent data shows that you can find tickets from as low as $333 on this airline. An additional option worth looking into is Southwest, starting at $372. Frontier is priced at 12% lower than the current average price of a flight leaving 3 months from now.
Can I find deals for flights from St. Louis to Islip that include hotel bookings?
Yes. In addition to deals on St. Louis to Islip flights, Cheapflights offers vacation packages that include both flights and hotel.
How can I find direct flights from St. Louis to Islip?
After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from St. Louis to Islip.
Can I find deals for business class flights from St. Louis to Islip?
Yes. Cheapflights offers flight deals from St. Louis to Islip 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 St. Louis to Islip, New York?
Currently, January is the cheapest month in which you can book a flight from St. Louis to Islip, New York (average of $108). Flying from St. Louis to Islip, New York in November is currently the most expensive (average of $213). 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.

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Complete your trip

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Other flights to Islip

Top airline flying from St. Louis to Islip

Airline	Cheapest	Average	Flexibility	On-time
Southwest	Cheapest$339	Average$396	FlexibilityNo cancel fee	On-time63%

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$137+ Cheap flights from St. Louis to Islip, NY (STL - ISP)

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 9/7. Fares are subject to change and may not be available on all flights or dates of travel.

Find cheap flights from St. Louis to Islip with Cheapflights

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2. Select your favorite providers

3. Compare prices and book

Cheap flight deals from St. Louis to Islip

Round-trip from

One-way from

Popular in

Cheapest in

Average price

Find flight deals from St. Louis to Islip

Cheapest flights from St. Louis to IslipExplore the most affordable flight options available from St. Louis to Islip. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 3, 2025.

Explore the most affordable flight options available from St. Louis to Islip. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 3, 2025.

Cheapflights Fare Finder

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

Best time to book a flight from St. Louis to Islip

Have a flexible travel schedule? Discover the best time to fly to Islip from St. Louis with our price prediction graph.

Cheapflights Insights

Everything you need to know about your flight from St. Louis to Islip

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

What is the cheapest time of day to fly from STL to ISP?

Find hourly flight availability from St. Louis to Islip. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated July 3, 2025.

Reviews of airlines servicing Islip

Get insights into the airlines that provide service to Islip. 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 Islip. Reviews last updated July 3, 2025.

Peruse reviews from past customers who have flown with Southwest and Frontier from St. Louis to Islip to help guide your decision. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.

Related info for your journey

Find useful and relevant information for your journey from St. Louis to Islip. 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 St. Louis to Islip, New York round-trip?

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

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

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

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

Traveling to a place near St. Louis?

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Top airline flying from St. Louis to Islip

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Cheapest flights from St. Louis to Islip
Explore the most affordable flight options available from St. Louis to Islip. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 3, 2025.