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Cheap flights from Islip to St. Louis from $147

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 10/30. 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

Enter your travel dates to find the best prices.
Southwest Logo
3:55 pm - 10:00 pmISP-STL
7h 05m1 stop
Southwest Logo
9:40 am - 3:20 pmSTL-ISP
4h 40m1 stop
$239Southwest
Find Deal
Wed, Dec 10 - Wed, Dec 17
Southwest Logo
5:40 am - 3:50 pmISP-STL
11h 10m1 stop
Southwest Logo
9:40 am - 3:20 pmSTL-ISP
4h 40m1 stop
$244Southwest
Find Deal
Wed, Nov 19 - Wed, Dec 10
Southwest Logo
5:40 am - 12:35 pmISP-STL
7h 55m2 stops
Southwest Logo
7:00 am - 3:20 pmSTL-ISP
7h 20m2 stops
$249Southwest
Find Deal
Wed, Nov 19 - Wed, Dec 10
Frontier Logo
6:37 pm - 1:17 pmISP-STL
19h 40m1 stop
Frontier Logo
7:45 pm - 5:42 pmSTL-ISP
20h 57m2 stops
$278Frontier
Find Deal
Thu, Oct 30 - Mon, Nov 3
Frontier Logo
6:37 pm - 1:17 pmISP-STL
19h 40m1 stop
Frontier Logo
7:45 pm - 5:42 pmSTL-ISP
20h 57m2 stops
$282Frontier
Find Deal
Thu, Oct 30 - Mon, Nov 3
Southwest Logo
1:10 pm - 7:50 pmISP-STL
7h 40m1 stop
Southwest Logo
6:05 am - 12:15 pmSTL-ISP
5h 10m1 stop
$305Southwest
Find Deal
Wed, Oct 29 - Wed, Nov 5
Southwest Logo
6:00 am - 11:25 amISP-STL
6h 25m1 stop
Southwest Logo
7:00 am - 3:20 pmSTL-ISP
7h 20m2 stops
$310Southwest
Find Deal
Wed, Oct 29 - Wed, Nov 5
Frontier Logo
6:37 pm - 1:17 pmISP-STL
19h 40m1 stop
Frontier Logo
2:12 pm - 5:42 pmSTL-ISP
26h 30m1 stop
$311Frontier
Find Deal
Thu, Oct 30 - Mon, Nov 3
Southwest Logo
6:00 am - 1:50 pmISP-STL
8h 50m2 stops
Southwest Logo
7:00 am - 3:20 pmSTL-ISP
7h 20m2 stops
$315Southwest
Find Deal
Wed, Oct 29 - Wed, Nov 5
Multiple Airlines Logo
7:30 am - 3:49 pmISP-STL
9h 19m2 stops
Multiple Airlines Logo
7:00 am - 7:45 pmSTL-ISP
11h 45m2 stops
$915Multiple Airlines
Find Deal
Wed, Nov 19 - Wed, Dec 10

Southwest flights from Islip to St. Louis

Our best Southwest deals on Islip to St. Louis flight tickets
Southwest
Dec 10
ISP3:55 pmIslip Long Island
7h 05m
1 stop
STL10:00 pmLambert-St Louis
Dec 17
STL9:40 amLambert-St Louis
4h 40m
1 stop
ISP3:20 pmIslip Long Island
$239
Find similar
Southwest
Nov 19
ISP5:40 amIslip Long Island
11h 10m
1 stop
STL3:50 pmLambert-St Louis
Dec 10
STL9:40 amLambert-St Louis
4h 40m
1 stop
ISP3:20 pmIslip Long Island
$244
Find similar
Southwest
Nov 19
ISP5:40 amIslip Long Island
7h 55m
2 stops
STL12:35 pmLambert-St Louis
Dec 10
STL7:00 amLambert-St Louis
7h 20m
2 stops
ISP3:20 pmIslip Long Island
$249
Find similar

Frontier flights from Islip to St. Louis

Our best Frontier deals on Islip to St. Louis flight tickets
Frontier
Oct 30
ISP6:37 pmIslip Long Island
19h 40m
1 stop
STL1:17 pmLambert-St Louis
Nov 3
STL7:45 pmLambert-St Louis
20h 57m
2 stops
ISP5:42 pmIslip Long Island
$278
Find similar
Frontier
Oct 30
ISP6:37 pmIslip Long Island
19h 40m
1 stop
STL1:17 pmLambert-St Louis
Nov 3
STL7:45 pmLambert-St Louis
20h 57m
2 stops
ISP5:42 pmIslip Long Island
$282
Find similar
Frontier
Oct 30
ISP6:37 pmIslip Long Island
19h 40m
1 stop
STL1:17 pmLambert-St Louis
Nov 3
STL2:12 pmLambert-St Louis
26h 30m
1 stop
ISP5:42 pmIslip Long Island
$311
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 October 16, 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

Wed 12/10

3:55 pm-10:00 pm

1 stop7h 05m

Lambert-St Louis

Wed 12/17

9:40 am-3:20 pm

1 stop4h 40m

$239

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 11/19

5:40 am-3:50 pm

1 stop11h 10m

Lambert-St Louis

Wed 12/10

9:40 am-3:20 pm

1 stop4h 40m

$244

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 11/19

5:40 am-12:35 pm

2 stops7h 55m

Lambert-St Louis

Wed 12/10

7:00 am-3:20 pm

2 stops7h 20m

$249

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 10/30

6:37 pm-1:17 pm

1 stop19h 40m

Lambert-St Louis

Mon 11/3

7:45 pm-5:42 pm

2 stops20h 57m

$278

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 10/30

6:37 pm-1:17 pm

1 stop19h 40m

Lambert-St Louis

Mon 11/3

7:45 pm-5:42 pm

2 stops20h 57m

$282

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 10/29

1:10 pm-7:50 pm

1 stop7h 40m

Lambert-St Louis

Wed 11/5

6:05 am-12:15 pm

1 stop5h 10m

$305

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 10/29

6:00 am-11:25 am

1 stop6h 25m

Lambert-St Louis

Wed 11/5

7:00 am-3:20 pm

2 stops7h 20m

$310

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 10/30

6:37 pm-1:17 pm

1 stop19h 40m

Lambert-St Louis

Mon 11/3

2:12 pm-5:42 pm

1 stop26h 30m

$311

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 10/29

6:00 am-1:50 pm

2 stops8h 50m

Lambert-St Louis

Wed 11/5

7:00 am-3:20 pm

2 stops7h 20m

$315

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 11/19

7:30 am-3:49 pm

2 stops9h 19m

Lambert-St Louis

Wed 12/10

7:00 am-7:45 pm

2 stops11h 45m

$915

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 16 resultsSorted by cheapest first
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See travel insights to St. Louis from

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 $322. 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 $434. 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 $346 when looking at flights departing in the morning. In the evening is when there is more demand to fly to St. Louis, so prices are often more expensive at around $375 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 6h 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 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
4,241 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
Wentzville
Collinsville
Fenton
St. Peters
Alton
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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