How long is the flight from Islip to St. Louis?

There are many flights that can get you from Islip to St. Louis in 17h 09m. Fly via Frontier to get the fastest option. Airlines will cover a distance of 926 mi.

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.

In terms of precipitation, rainfall in St. Louis ranges from 2.2 - 4.7 inches per month. May is typically the wettest month, when rainfall can reach 4.7 in. February is typically the driest time to visit St. Louis when rainfall is around 2.2 in.

If weather is an important factor for your trip to St. Louis, 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 80.6 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 32.0 F).

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

To save up to 64% on this flight, we recommend booking at least 57 days prior to travel. The price may fluctuate and will likely increase closer to your departure date. Users on Cheapflights have found tickets from Islip to St. Louis from $333 1-2 weeks out and tickets from $390 for flights departing within the next 72 hours.

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

Due to multiple factors, expect to potentially pay more when booking in December. For low rates, January can be a great choice for travel to St. Louis. Flights to St. Louis from Islip in January are about $334 on average during January, but can be found for as low as $207.

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.

$79+ Cheap Flights from Islip to St. Louis

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Cheap flight deals from Islip to St. Louis

Round-trip from	$235 (Frontier)
One-way from	$79 (Cheapflightsfares)
Popular in	May
Cheapest in	July
Average price	$310

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. 12% potential increase in price ($52 potential increase over avg. RT price).

Search Deals

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 9, 2025.

Mon 10/274:58 pmISP - STL

2 stops17h 09mFrontier

Fri 10/314:52 pmSTL - ISP

2 stops16h 45mFrontier

Deal found 9/7

$235

Wed 9/2411:35 amISP - STL

2 stops28h 29mFrontier

Sun 9/2810:39 amSTL - ISP

2 stops47h 01mFrontier

Deal found 9/8

$239

Fri 10/35:05 pmISP - STL

2 stops17h 01mFrontier

Mon 10/67:55 pmSTL - ISP

2 stops17h 18mFrontier

Deal found 9/7

$245

Tue 9/2311:25 amISP - STL

2 stops47h 29mFrontier

Thu 9/257:55 pmSTL - ISP

2 stops38h 00mFrontier

Deal found 9/8

$250

Sat 10/1812:38 pmISP - STL

1 stop6h 24mFrontier

Sun 10/191:41 pmSTL - ISP

1 stop6h 11mFrontier

Deal found 9/8

$280

Sun 12/75:30 pmISP - STL

1 stop6h 45mSouthwest

Tue 12/166:05 amSTL - ISP

1 stop5h 10mSouthwest

Deal found 9/7

$282

Sun 12/79:09 pmISP - STL

1 stop12h 36mFrontier

Wed 12/175:11 pmSTL - ISP

1 stop25h 10mFrontier

Deal found 9/7

$334

Mon 9/225:05 pmISP - STL

2 stops17h 01mFrontier

Fri 9/267:55 pmSTL - ISP

2 stops14h 00mFrontier

Deal found 9/7

$344

Best flights from Islip to St. Louis
Discover carefully curated flight deals from Islip to St. Louis that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated September 9, 2025.

Mon 10/274:58 pmISP - STL

2 stops17h 09mFrontier

Fri 10/314:52 pmSTL - ISP

2 stops16h 45mFrontier

Deal found 9/7

$235

Sun 12/75:30 pmISP - STL

1 stop6h 45mSouthwest

Tue 12/166:05 amSTL - ISP

1 stop5h 10mSouthwest

Deal found 9/7

$282

Wed 9/2411:35 amISP - STL

2 stops28h 29mFrontier

Sun 9/2810:39 amSTL - ISP

2 stops47h 01mFrontier

Deal found 9/8

$239

Fri 10/35:05 pmISP - STL

2 stops17h 01mFrontier

Mon 10/67:55 pmSTL - ISP

2 stops17h 18mFrontier

Deal found 9/7

$245

Sat 10/1812:38 pmISP - STL

1 stop6h 24mFrontier

Sun 10/191:41 pmSTL - ISP

1 stop6h 11mFrontier

Deal found 9/8

$280

Sun 12/79:09 pmISP - STL

1 stop12h 36mFrontier

Wed 12/175:11 pmSTL - ISP

1 stop25h 10mFrontier

Deal found 9/7

$334

Mon 9/225:05 pmISP - STL

2 stops17h 01mFrontier

Fri 9/267:55 pmSTL - ISP

2 stops14h 00mFrontier

Deal found 9/7

$344

Sat 10/45:05 pmISP - STL

2 stops17h 01mFrontier

Tue 10/77:52 pmSTL - ISP

2 stops17h 21mFrontier

Deal found 9/9

$365

Last-minute flights from Islip to St. Louis
Discover last-minute flight deals from Islip to St. Louis. Data last updated September 9, 2025 and is based on user searches.

Mon 9/225:05 pmISP - STL

2 stops17h 01mFrontier

Fri 9/267:55 pmSTL - ISP

2 stops14h 00mFrontier

Deal found 9/7

$344

Tue 9/2311:25 amISP - STL

2 stops47h 29mFrontier

Thu 9/257:55 pmSTL - ISP

2 stops38h 00mFrontier

Deal found 9/8

$250

Wed 9/2411:35 amISP - STL

2 stops28h 29mFrontier

Sun 9/2810:39 amSTL - ISP

2 stops47h 01mFrontier

Deal found 9/8

$239

Fri 10/35:05 pmISP - STL

2 stops17h 01mFrontier

Mon 10/67:55 pmSTL - ISP

2 stops17h 18mFrontier

Deal found 9/7

$245

Sat 10/45:05 pmISP - STL

2 stops17h 01mFrontier

Tue 10/77:52 pmSTL - ISP

2 stops17h 21mFrontier

Deal found 9/9

$365

Sat 10/45:05 pmISP - STL

2 stops17h 01mFrontier

Mon 10/67:55 pmSTL - ISP

2 stops17h 18mFrontier

Deal found 9/9

$377

Sat 10/1812:38 pmISP - STL

1 stop6h 24mFrontier

Sun 10/191:41 pmSTL - ISP

1 stop6h 11mFrontier

Deal found 9/8

$280

Mon 10/274:58 pmISP - STL

2 stops17h 09mFrontier

Fri 10/314:52 pmSTL - ISP

2 stops16h 45mFrontier

Deal found 9/7

$235

One-way flights from Islip to St. Louis
Search for one-way flight options from Islip to St. Louis. Find affordable one-way fares based on user searches. Data last updated September 9, 2025.

Sat 10/2512:38 pmISP - STL

1 stop6h 24mFrontier

Deal found 9/8

$79

Sat 10/1812:38 pmISP - STL

1 stop6h 24mFrontier

Deal found 9/8

$115

Mon 12/812:55 pmISP - STL

1 stop10h 05mSouthwest

Deal found 9/8

$116

Sat 10/1112:00 pmISP - STL

1 stop7h 02mFrontier

Deal found 9/8

$145

Sun 11/29:27 pmISP - STL

1 stop13h 13mFrontier

Deal found 9/9

$154

Fri 10/103:20 pmISP - STL

1 stop6h 15mSouthwest

Deal found 9/8

$209

Mon 12/810:06 amISP - STL

3 stops33h 30mMultiple Airlines

Deal found 9/8

$221

Fri 10/108:47 pmISP - STL

3 stops38h 50mMultiple Airlines

Deal found 9/8

$300

Fly from

Fly to

Route

Depart

Return

Price

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 10/27

4:58 pm-9:07 am

2 stops17h 09m

Lambert-St Louis

Fri 10/31

4:52 pm-10:37 am

2 stops16h 45m

$235

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 9/24

11:35 am-3:04 pm

2 stops28h 29m

Lambert-St Louis

Sun 9/28

10:39 am-10:40 am

2 stops47h 01m

$239

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

$245

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sat 10/18

12:38 pm-6:02 pm

1 stop6h 24m

Lambert-St Louis

Sun 10/19

1:41 pm-8:52 pm

1 stop6h 11m

$280

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sun 12/7

5:30 pm-11:15 pm

1 stop6h 45m

Lambert-St Louis

Tue 12/16

6:05 am-12:15 pm

1 stop5h 10m

$282

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sun 12/7

9:09 pm-8:45 am

1 stop12h 36m

Lambert-St Louis

Wed 12/17

5:11 pm-7:21 pm

1 stop25h 10m

$334

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 9/22

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Fri 9/26

7:55 pm-10:55 am

2 stops14h 00m

$344

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

$365

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sat 10/25

12:38 pm-6:02 pm

1 stop6h 24m

$79

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sat 10/18

12:38 pm-6:02 pm

1 stop6h 24m

$115

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/7

Showing 1-10 of 14 results

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?

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

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

4,250 reviews

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

4,250 reviews

Southwest

8.0

Very good

4,250 reviews

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

How long is the flight from Islip to St. Louis?
There are many flights that can get you from Islip to St. Louis in 17h 09m. Fly via Frontier to get the fastest option. Airlines will cover a distance of 926 mi.
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

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

Top airline flying from Islip to St. Louis

Airline	Cheapest	Average	Flexibility	On-time
Southwest	Cheapest$304	Average$391	FlexibilityNo cancel fee	On-time63%

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$79+ 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 10/25. Fares are subject to change and may not be available on all flights or dates of travel.

Find cheap flights from Islip to St. Louis with Cheapflights

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Cheap flight deals from Islip to St. Louis

Round-trip from

One-way from

Popular in

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Find flight deals from Islip to St. Louis

Cheapest flights from Islip to St. LouisExplore 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 9, 2025.

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 9, 2025.

Cheapflights Fare Finder

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

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.

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?

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

Reviews of airlines servicing St. Louis

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.

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?

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

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

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

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

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

Traveling to a place near St. Louis?

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

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

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Book with Flexibility

Travel Smart

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 9, 2025.