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Cheap flights from Islip, New York to St. Louis from $144

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 8/7. 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
$285Frontier
Fri, Jul 24 - Fri, Jul 31
Southwest Logo
6:20 am - 11:50 am
ISP
-
STL
6h 30m
1 stop
Southwest Logo
6:05 am - 12:35 pm
STL
-
ISP
5h 30m
1 stop
$295Southwest
Sun, Aug 23 - Mon, Aug 31
Southwest Logo
6:00 pm - 11:15 pm
ISP
-
STL
6h 15m
1 stop
Southwest Logo
6:55 am - 1:45 pm
STL
-
ISP
5h 50m
1 stop
$296Southwest
Thu, Jul 9 - Wed, Jul 15
Southwest Logo
6:10 pm - 11:25 pm
ISP
-
STL
6h 15m
1 stop
Southwest Logo
12:55 pm - 10:05 pm
STL
-
ISP
8h 10m
2 stops
$300Southwest
Sun, Aug 23 - Mon, Aug 31
Southwest Logo
6:00 pm - 12:40 am
ISP
-
STL
7h 40m
2 stops
Southwest Logo
6:55 am - 1:45 pm
STL
-
ISP
5h 50m
1 stop
$301Southwest
Thu, Jul 9 - Wed, Jul 15
Frontier Logo
9:52 pm - 11:49 pm
ISP
-
STL
26h 57m
1 stop
Frontier Logo
4:17 pm - 8:57 pm
STL
-
ISP
27h 40m
1 stop
$302Frontier
Fri, Jun 26 - Tue, Jun 30
Southwest Logo
6:20 am - 3:50 pm
ISP
-
STL
10h 30m
2 stops
Southwest Logo
2:45 pm - 10:05 pm
STL
-
ISP
6h 20m
2 stops
$311Southwest
Sun, Aug 23 - Mon, Aug 31
Southwest Logo
3:05 pm - 8:20 pm
ISP
-
STL
6h 15m
1 stop
Southwest Logo
4:30 pm - 11:45 pm
STL
-
ISP
6h 15m
1 stop
$313Southwest
Fri, Jul 10 - Mon, Jul 13
Southwest Logo
3:05 pm - 8:50 pm
ISP
-
STL
6h 45m
2 stops
Southwest Logo
4:30 pm - 11:45 pm
STL
-
ISP
6h 15m
1 stop
$318Southwest
Fri, Jul 10 - Mon, Jul 13
Southwest Logo
6:00 pm - 10:50 pm
ISP
-
STL
5h 50m
2 stops
Southwest Logo
2:30 pm - 11:40 pm
STL
-
ISP
8h 10m
2 stops
$323Southwest
Fri, Jul 10 - Mon, Jul 13

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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 24
ISP10:57 amIslip Long Island
14h 02m
1 stop
STL11:59 pmLambert-St Louis
Jul 31
STL4:09 pmLambert-St Louis
16h 44m
1 stop
ISP9:53 amIslip Long Island
$285
Frontier
Jun 26
ISP9:52 pmIslip Long Island
26h 57m
1 stop
STL11:49 pmLambert-St Louis
Jun 30
STL4:17 pmLambert-St Louis
27h 40m
1 stop
ISP8:57 pmIslip Long Island
$302
Frontier
Jun 25
ISP9:52 pmIslip Long Island
26h 57m
1 stop
STL11:49 pmLambert-St Louis
Jul 5
STL4:09 pmLambert-St Louis
16h 44m
1 stop
ISP9:53 amIslip Long Island
$348

Southwest flights from Islip, New York to St. Louis

Our best Southwest deals on Islip, New York to St. Louis flight tickets
Southwest
Aug 23
ISP6:20 amIslip Long Island
6h 30m
1 stop
STL11:50 amLambert-St Louis
Aug 31
STL6:05 amLambert-St Louis
5h 30m
1 stop
ISP12:35 pmIslip Long Island
$295
Southwest
Jul 9
ISP6:00 pmIslip Long Island
6h 15m
1 stop
STL11:15 pmLambert-St Louis
Jul 15
STL6:55 amLambert-St Louis
5h 50m
1 stop
ISP1:45 pmIslip Long Island
$296
Southwest
Aug 23
ISP6:10 pmIslip Long Island
6h 15m
1 stop
STL11:25 pmLambert-St Louis
Aug 31
STL12:55 pmLambert-St Louis
8h 10m
2 stops
ISP10:05 pmIslip Long Island
$300

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 11, 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

Fri 7/24

10:57 am-11:59 pm

1 stop14h 02m

Lambert-St Louis

Fri 7/31

4:09 pm-9:53 am

1 stop16h 44m

$285
Quickest round-trip

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sun 8/23

6:20 am-11:50 am

1 stop6h 30m

Lambert-St Louis

Mon 8/31

6:05 am-12:35 pm

1 stop5h 30m

$295

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 7/9

6:00 pm-11:15 pm

1 stop6h 15m

Lambert-St Louis

Wed 7/15

6:55 am-1:45 pm

1 stop5h 50m

$296

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sun 8/23

6:10 pm-11:25 pm

1 stop6h 15m

Lambert-St Louis

Mon 8/31

12:55 pm-10:05 pm

2 stops8h 10m

$300

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 7/9

6:00 pm-12:40 am

2 stops7h 40m

Lambert-St Louis

Wed 7/15

6:55 am-1:45 pm

1 stop5h 50m

$301

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 6/26

9:52 pm-11:49 pm

1 stop26h 57m

Lambert-St Louis

Tue 6/30

4:17 pm-8:57 pm

1 stop27h 40m

$302

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sun 8/23

6:20 am-3:50 pm

2 stops10h 30m

Lambert-St Louis

Mon 8/31

2:45 pm-10:05 pm

2 stops6h 20m

$311

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 7/10

3:05 pm-8:20 pm

1 stop6h 15m

Lambert-St Louis

Mon 7/13

4:30 pm-11:45 pm

1 stop6h 15m

$313

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 7/10

3:05 pm-8:50 pm

2 stops6h 45m

Lambert-St Louis

Mon 7/13

4:30 pm-11:45 pm

1 stop6h 15m

$318

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 7/10

6:00 pm-10:50 pm

2 stops5h 50m

Lambert-St Louis

Mon 7/13

2:30 pm-11:40 pm

2 stops8h 10m

$323

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 18 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 $366. 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 $482. 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 $381 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 $403 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

6h 15m

Direct flights

None
The fastest flight from Islip, New York to St. Louis takes 6h 15m
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 6h 15m.

  • 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 many operators does momondo search for flights from Islip Long Island Airport to Lambert-St Louis Airport?

  • 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.

  • What is the most popular airline from Islip, New York to St. Louis?

Best airlines flying from Islip, New York to St. Louis

Compare and see reviews for airlines that fly from Islip, New York to St. Louis with momondo
Airline
Rating
Free Cancellation
Price
SouthwestPriceFrom $259Free CancellationRating
7.9
4,235 reviews
Search Southwest flights

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
St. Peters
Collinsville
Alton
Wentzville
Fenton
Clayton
Farmington
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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