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Cheap flights from Islip, New York to St. Louis from $150

This is the cheapest one-way flight price found by a momondo user in the last 72 hours by searching for a flight from Islip, New York to St. Louis departing on 8/6. Fares may change, and may not be available for all flights or travel dates. Click the price to refresh the search for this deal.
1 adult
1 adult, Economy, 0 bags

Find the cheapest flights from Islip, New York to St. Louis

Cheap round-trip flights

Enter your travel dates to find the best prices.
Frontier Logo
10:57 am - 11:59 pm
ISP
-
STL
14h 02m
1 stop
Frontier Logo
4:09 pm - 9:53 am
STL
-
ISP
16h 44m
1 stop
$249Frontier
Wed, Jul 29 - Fri, Aug 7
Southwest Logo
4:05 pm - 9:40 pm
ISP
-
STL
6h 35m
1 stop
Southwest Logo
5:55 am - 12:10 pm
STL
-
ISP
5h 15m
1 stop
$273Southwest
Mon, Sep 14 - Wed, Sep 16
Southwest Logo
4:05 pm - 9:40 pm
ISP
-
STL
6h 35m
1 stop
Southwest Logo
10:45 am - 9:05 pm
STL
-
ISP
9h 20m
2 stops
$278Southwest
Mon, Sep 14 - Wed, Sep 16
Southwest Logo
4:05 pm - 10:05 pm
ISP
-
STL
7h 00m
2 stops
Southwest Logo
10:45 am - 9:05 pm
STL
-
ISP
9h 20m
2 stops
$283Southwest
Mon, Sep 14 - Wed, Sep 16
Southwest Logo
5:50 pm - 11:15 pm
ISP
-
STL
6h 25m
1 stop
Southwest Logo
3:45 pm - 11:15 pm
STL
-
ISP
6h 30m
2 stops
$300Southwest
Thu, Jul 16 - Sat, Jul 18
Southwest Logo
5:50 pm - 10:50 pm
ISP
-
STL
6h 00m
2 stops
Southwest Logo
3:45 pm - 11:15 pm
STL
-
ISP
6h 30m
2 stops
$305Southwest
Thu, Jul 16 - Sat, Jul 18
Southwest Logo
12:25 pm - 8:30 pm
ISP
-
STL
9h 05m
2 stops
Southwest Logo
4:15 pm - 10:05 pm
STL
-
ISP
4h 50m
1 stop
$317Southwest
Wed, Jul 29 - Fri, Aug 7
Southwest Logo
5:00 pm - 10:25 pm
ISP
-
STL
6h 25m
1 stop
Southwest Logo
7:20 am - 3:55 pm
STL
-
ISP
7h 35m
1 stop
$318Southwest
Fri, Aug 28 - Sun, Aug 30
Southwest Logo
4:05 pm - 10:05 pm
ISP
-
STL
7h 00m
2 stops
Southwest Logo
7:20 am - 3:55 pm
STL
-
ISP
7h 35m
1 stop
$324Southwest
Fri, Aug 28 - Sun, Aug 30
Southwest Logo
6:05 pm - 12:10 am
ISP
-
STL
7h 05m
1 stop
Southwest Logo
5:10 pm - 11:40 pm
STL
-
ISP
5h 30m
1 stop
$343Southwest
Thu, Jul 16 - Sun, Jul 19

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Frontier flights from Islip, New York to St. Louis

Our best Frontier deals on Islip, New York to St. Louis flight tickets
Frontier
Jul 29
ISP10:57 amIslip Long Island
14h 02m
1 stop
STL11:59 pmLambert-St Louis
Aug 7
STL4:09 pmLambert-St Louis
16h 44m
1 stop
ISP9:53 amIslip Long Island
$249
Frontier
Jun 27
ISP9:52 pmIslip Long Island
26h 57m
1 stop
STL11:49 pmLambert-St Louis
Jul 1
STL4:17 pmLambert-St Louis
16h 46m
1 stop
ISP10:03 amIslip Long Island
$403
Frontier
Jul 6
ISP10:57 amIslip Long Island
14h 02m
1 stop
STL11:59 pmLambert-St Louis
Jul 9
STL4:09 pmLambert-St Louis
16h 44m
1 stop
ISP9:53 amIslip Long Island
$547

Southwest flights from Islip, New York to St. Louis

Our best Southwest deals on Islip, New York to St. Louis flight tickets
Southwest
Sep 14
ISP4:05 pmIslip Long Island
6h 35m
1 stop
STL9:40 pmLambert-St Louis
Sep 16
STL5:55 amLambert-St Louis
5h 15m
1 stop
ISP12:10 pmIslip Long Island
$273
Southwest
Sep 14
ISP4:05 pmIslip Long Island
6h 35m
1 stop
STL9:40 pmLambert-St Louis
Sep 16
STL10:45 amLambert-St Louis
9h 20m
2 stops
ISP9:05 pmIslip Long Island
$278
Southwest
Sep 14
ISP4:05 pmIslip Long Island
7h 00m
2 stops
STL10:05 pmLambert-St Louis
Sep 16
STL10:45 amLambert-St Louis
9h 20m
2 stops
ISP9:05 pmIslip Long Island
$283

momondo Fare Finder

 
Customize your flight search to find flights from Islip, New York 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, momondo users made 832,500 searches. Data last updated June 24, 2026.
Use the filters below to find and compare flights from Islip, New York 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

Wed 7/29

10:57 am-11:59 pm

1 stop14h 02m

Lambert-St Louis

Fri 8/7

4:09 pm-9:53 am

1 stop16h 44m

$249
Quickest round-trip

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 9/14

4:05 pm-9:40 pm

1 stop6h 35m

Lambert-St Louis

Wed 9/16

5:55 am-12:10 pm

1 stop5h 15m

$273

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 9/14

4:05 pm-9:40 pm

1 stop6h 35m

Lambert-St Louis

Wed 9/16

10:45 am-9:05 pm

2 stops9h 20m

$278

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 9/14

4:05 pm-10:05 pm

2 stops7h 00m

Lambert-St Louis

Wed 9/16

10:45 am-9:05 pm

2 stops9h 20m

$283

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 7/16

5:50 pm-11:15 pm

1 stop6h 25m

Lambert-St Louis

Sat 7/18

3:45 pm-11:15 pm

2 stops6h 30m

$300

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 7/16

5:50 pm-10:50 pm

2 stops6h 00m

Lambert-St Louis

Sat 7/18

3:45 pm-11:15 pm

2 stops6h 30m

$305

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 7/29

12:25 pm-8:30 pm

2 stops9h 05m

Lambert-St Louis

Fri 8/7

4:15 pm-10:05 pm

1 stop4h 50m

$317

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 8/28

5:00 pm-10:25 pm

1 stop6h 25m

Lambert-St Louis

Sun 8/30

7:20 am-3:55 pm

1 stop7h 35m

$318

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 8/28

4:05 pm-10:05 pm

2 stops7h 00m

Lambert-St Louis

Sun 8/30

7:20 am-3:55 pm

1 stop7h 35m

$324

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 7/16

6:05 pm-12:10 am

1 stop7h 05m

Lambert-St Louis

Sun 7/19

5:10 pm-11:40 pm

1 stop5h 30m

$343

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 14 resultsSorted by cheapest first
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See travel insights to St. Louis from

How to get the cheapest flight ticket from Islip, New York to St. Louis

Look no further. We've gone through all the searches for this route on momondo so you have the important information and insights to find the cheapest flight ticket for your trip

What is the cheapest day to depart on your flight to St. Louis?

The cheapest day to depart on your flight to St. Louis is on a Wednesday when prices can be found for as low as $369. This is often the case because there is less demand to fly during this day of the week. If your travel schedule is flexible, try to avoid departing on a Sunday because tickets tend to average around $483. These prices are subject to change though, so be sure to set up a Price Alert for flights to St. Louis.

What is the cheapest time of day to depart on your flight to St. Louis?

Flying to St. Louis from Islip, New York in the evening is the least expensive time of day to depart. momondo users have found prices as low as $383 when looking at flights departing in the evening. At noon is when there is more demand to fly to St. Louis, so prices are often more expensive at around $412 per ticket.

When to book flights from Islip, New York to St. Louis

Are you open to changing your travel dates? Check out the ideal times to fly from Islip, New York to St. Louis according to our flight data. Find out which month and days have the cheapest flights.
Estimated round-trip price

Cheap Islip, New York to St. Louis (ISP to STL) flight deals and tips

Find info about flight duration, direct flights, and airports for your flight from Islip, New York to St. Louis

Fastest flight time

5h 25m

Direct flights

None
The fastest flight from Islip, New York to St. Louis takes 5h 25m
There are no direct flights from Islip, New York to St. Louis. There are no popular flight routes from Islip, New York to St. Louis.
Search flight deals

Frequently asked questions about flying from Islip, New York to St. Louis

  • How far is Islip Long Island to Lambert-St Louis by plane?

    There are 912.8 mi between Islip Long Island and Lambert-St Louis. In terms of flight time, this usually takes a little over 5h 25m.

  • When did momondo last update prices for flights from Islip Long Island Airport to Lambert-St Louis Airport?

    Prices for flights from Islip Long Island Airport to Lambert-St Louis Airport are refreshed on a daily basis.

  • How old do you have to be to fly from Islip Long Island Airport to Lambert-St Louis Airport?

    The minimum age for a child to fly alone is five, but airlines that offer an unaccompanied minor (UNMR) service may have their own age limitations. Flight duration, scheduling, and layovers are among the considerations that may influence age limits. We recommend that you double-check with the airline you are booking with for travel from Islip Long Island Airport to Lambert-St Louis Airport.

  • What documentation or ID do you need to fly to Lambert-St Louis Airport?

    The travel and health documents you'll need for your trip to Lambert-St Louis Airport may differ based on your itinerary and personal situation. Typically, you should have several documents on hand, such as a national ID card or driver's license and a passport that is valid for six months after your intended arrival at Lambert-St Louis Airport. It is always advisable to seek advice from your airline or a trusted third party, such as IATA.

Traveling to a place near St. Louis?

Book flights to St. Louis if you plan to visit one of these locations
St. Charles
Chesterfield
Fairview Heights
Hermann
Maryland Heights
Florissant
O'Fallon
Collinsville
St. Peters
Alton
Wentzville
Farmington
Fenton
Clayton
Festus
Eureka
Litchfield
Edwardsville
Grafton
Shrewsbury

Why use momondo?

Why should I use momondo to find a flight deal from Islip to St. Louis?

momondo compares prices from hundreds of airlines and agents so you can find and book the best deal on flights from Islip to St. Louis. Millions of users trust and use momondo every year so you are in good hands.

Can I find flights from Islip to St. Louis with flexible booking policies on momondo?

Yes. momondo allows you to filter the results for Islip to St. Louis flights to just show those with flexible booking policies.

How can momondo help me find flights from Islip to St. Louis?

momondo offers useful filters to help you find the right flight. Choose specific flight times, airports or even what payment method you prefer. We have numerous options to help you book your ideal flight from Islip to St. Louis.

I’m not ready to book a flight from Islip to St. Louis right now. Can momondo alert me if prices change?

Price alerts on flights to St. Louis from Islip are quick and easy to set up on momondo. Simply perform a search and select the price alert feature. It is as simple as that.

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