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Cheap flights from Islip to St. Louis from $80

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 to St. Louis departing on 10/25. Fares may change, and may not be available for all flights or travel dates. Click the price to refresh the search for this deal.
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Find the cheapest flights from Islip to St. Louis

Cheap round-trip flights

Frontier Logo
5:05 pm - 9:06 amISP-STL
17h 01m2 stops
Frontier Logo
9:32 pm - 10:55 amSTL-ISP
12h 23m1 stop
$202Frontier
Find Deal
Mon, Sep 29 - Fri, Oct 3
Southwest Logo
12:55 pm - 10:00 pmISP-STL
10h 05m1 stop
Southwest Logo
12:05 pm - 9:35 pmSTL-ISP
8h 30m1 stop
$222Southwest
Find Deal
Wed, Dec 3 - Tue, Dec 16
Southwest Logo
5:40 am - 12:35 pmISP-STL
7h 55m2 stops
Southwest Logo
12:45 pm - 9:35 pmSTL-ISP
7h 50m2 stops
$227Southwest
Find Deal
Wed, Dec 3 - Tue, Dec 16
Frontier Logo
11:40 am - 9:06 amISP-STL
22h 26m2 stops
Frontier Logo
10:39 am - 10:40 amSTL-ISP
23h 01m2 stops
$237Frontier
Find Deal
Thu, Oct 2 - Sun, Oct 5
Frontier Logo
4:58 pm - 9:07 amISP-STL
17h 09m2 stops
Frontier Logo
8:40 pm - 9:02 amSTL-ISP
11h 22m2 stops
$245Frontier
Find Deal
Mon, Oct 27 - Sat, Nov 1
Frontier Logo
11:40 am - 9:06 amISP-STL
22h 26m2 stops
Frontier Logo
7:55 pm - 9:04 amSTL-ISP
12h 09m2 stops
$246Frontier
Find Deal
Thu, Oct 2 - Sat, Oct 4
Frontier Logo
11:40 am - 9:06 amISP-STL
22h 26m2 stops
Frontier Logo
7:52 pm - 9:04 amSTL-ISP
12h 12m2 stops
$275Frontier
Find Deal
Thu, Oct 2 - Wed, Oct 8
Frontier Logo
9:09 pm - 8:45 amISP-STL
12h 36m1 stop
Frontier Logo
5:11 pm - 7:14 pmSTL-ISP
25h 03m1 stop
$279Frontier
Find Deal
Thu, Dec 4 - Tue, Dec 16
Logo
2:19 pm - 10:46 pmISP-STL
33h 27m2 stops
Logo
5:11 pm - 7:14 pmSTL-ISP
25h 03m1 stop
$281
Find Deal
Thu, Dec 4 - Mon, Dec 15
Southwest Logo
11:55 am - 8:30 pmISP-STL
9h 35m1 stop
Southwest Logo
4:55 pm - 11:45 pmSTL-ISP
5h 50m1 stop
$345Southwest
Find Deal
Sat, Oct 18 - Mon, Oct 20

Frontier flights from Islip to St. Louis

Our best Frontier deals on Islip to St. Louis flight tickets
Frontier
Sep 29
ISP5:05 pmIslip Long Island
17h 01m
2 stops
STL9:06 amLambert-St Louis
Oct 3
STL9:32 pmLambert-St Louis
12h 23m
1 stop
ISP10:55 amIslip Long Island
$202
Find similar
Frontier
Oct 2
ISP11:40 amIslip Long Island
22h 26m
2 stops
STL9:06 amLambert-St Louis
Oct 5
STL10:39 amLambert-St Louis
23h 01m
2 stops
ISP10:40 amIslip Long Island
$237
Find similar
Frontier
Oct 27
ISP4:58 pmIslip Long Island
17h 09m
2 stops
STL9:07 amLambert-St Louis
Nov 1
STL8:40 pmLambert-St Louis
11h 22m
2 stops
ISP9:02 amIslip Long Island
$245
Find similar

Southwest flights from Islip to St. Louis

Our best Southwest deals on Islip to St. Louis flight tickets
Southwest
Dec 3
ISP12:55 pmIslip Long Island
10h 05m
1 stop
STL10:00 pmLambert-St Louis
Dec 16
STL12:05 pmLambert-St Louis
8h 30m
1 stop
ISP9:35 pmIslip Long Island
$222
Find similar
Southwest
Dec 3
ISP5:40 amIslip Long Island
7h 55m
2 stops
STL12:35 pmLambert-St Louis
Dec 16
STL12:45 pmLambert-St Louis
7h 50m
2 stops
ISP9:35 pmIslip Long Island
$227
Find similar
Southwest
Oct 18
ISP11:55 amIslip Long Island
9h 35m
1 stop
STL8:30 pmLambert-St Louis
Oct 20
STL4:55 pmLambert-St Louis
5h 50m
1 stop
ISP11:45 pmIslip Long Island
$345
Find similar

momondo 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, momondo users made 832,500 searches. Data last updated September 15, 2025.
Use the filters below to find and compare flights from Islip to St. Louis that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 9/29

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Fri 10/3

9:32 pm-10:55 am

1 stop12h 23m

$202

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 12/3

12:55 pm-10:00 pm

1 stop10h 05m

Lambert-St Louis

Tue 12/16

12:05 pm-9:35 pm

1 stop8h 30m

$222

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 12/3

5:40 am-12:35 pm

2 stops7h 55m

Lambert-St Louis

Tue 12/16

12:45 pm-9:35 pm

2 stops7h 50m

$227

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 10/2

11:40 am-9:06 am

2 stops22h 26m

Lambert-St Louis

Sun 10/5

10:39 am-10:40 am

2 stops23h 01m

$237

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Mon 10/27

4:58 pm-9:07 am

2 stops17h 09m

Lambert-St Louis

Sat 11/1

8:40 pm-9:02 am

2 stops11h 22m

$245

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 10/2

11:40 am-9:06 am

2 stops22h 26m

Lambert-St Louis

Sat 10/4

7:55 pm-9:04 am

2 stops12h 09m

$246

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 10/2

11:40 am-9:06 am

2 stops22h 26m

Lambert-St Louis

Wed 10/8

7:52 pm-9:04 am

2 stops12h 12m

$275

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 12/4

9:09 pm-8:45 am

1 stop12h 36m

Lambert-St Louis

Tue 12/16

5:11 pm-7:14 pm

1 stop25h 03m

$279

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 12/4

2:19 pm-10:46 pm

2 stops33h 27m

Lambert-St Louis

Mon 12/15

5:11 pm-7:14 pm

1 stop25h 03m

$281

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Sat 10/18

11:55 am-8:30 pm

1 stop9h 35m

Lambert-St Louis

Mon 10/20

4:55 pm-11:45 pm

1 stop5h 50m

$345

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 20 resultsSorted by cheapest first
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How to get the cheapest flight ticket from Islip 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 $328. 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 $433. 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 in the morning is the least expensive time of day to depart. momondo users have found prices as low as $348 when looking at flights departing in the morning. At noon is when there is more demand to fly to St. Louis, so prices are often more expensive at around $385 per ticket.

When to book flights from Islip to St. Louis

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

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

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

Direct flights

None
There are no direct flights from Islip to St. Louis. There are no popular flight routes from Islip to St. Louis.
Search flight deals

  • 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 7h 55m.

  • 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 to St. Louis?

Best airlines flying from Islip to St. Louis

Compare and see reviews for airlines that fly from Islip to St. Louis with momondo
Airline
Rating
Free Cancellation
Price
SouthwestPriceFrom $304Free CancellationRating
8.0
4,242 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
Hermann
Fairview Heights
Florissant
Maryland Heights
O'Fallon
Fenton
Collinsville
Wentzville
Alton
St. Peters
Farmington
Festus
Glencoe
Clayton
Edwardsville
Eureka
Litchfield
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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