Latest deals
Insights
When to book
FAQs
Reviews
Price Alerts

Cheap flights from Islip to St. Louis from $79

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.
1 adult
0 bags

Save money when you book flights with momondo

Big names and deals

Big names and deals

Search 100s of travel sites to compare prices.

Filter for what you want

Filter for what you want

Free Wi-Fi? Stopover? Instantly customize your results.

Trusted and free

Trusted and free

We’re completely free to use - no hidden charges or fees.

Price Alerts

Price Alerts

Not ready to book? to track prices.
Search flight deals

Find the cheapest flights from Islip to St. Louis (ISP-STL)

Cheap round-trip flights

Frontier Logo
5:05 pm - 9:54 amISP-STL
41h 49m2 stops
Frontier Logo
9:32 pm - 10:55 amSTL-ISP
12h 23m1 stop
$201Frontier
Find Deal
Fri, Sep 26 - Fri, Oct 3
Frontier Logo
11:40 am - 1:02 pmISP-STL
26h 22m1 stop
Frontier Logo
1:52 pm - 10:40 amSTL-ISP
19h 48m1 stop
$234Frontier
Find Deal
Thu, Sep 25 - Sun, Sep 28
Frontier Logo
5:05 pm - 9:06 amISP-STL
17h 01m2 stops
Frontier Logo
4:00 pm - 10:40 amSTL-ISP
17h 40m2 stops
$235Frontier
Find Deal
Fri, Sep 26 - Mon, Sep 29
Frontier Logo
5:05 pm - 9:06 amISP-STL
17h 01m2 stops
Frontier Logo
10:39 am - 10:40 amSTL-ISP
23h 01m2 stops
$238Frontier
Find Deal
Fri, Sep 26 - Sun, Sep 28
Frontier Logo
11:40 am - 1:02 pmISP-STL
26h 22m1 stop
Frontier Logo
10:39 am - 10:40 amSTL-ISP
23h 01m2 stops
$243Frontier
Find Deal
Thu, Sep 25 - Sun, Sep 28
Frontier Logo
5:05 pm - 9:06 amISP-STL
17h 01m2 stops
Frontier Logo
7:55 pm - 10:55 amSTL-ISP
14h 00m2 stops
$246Frontier
Find Deal
Fri, Sep 26 - Fri, Oct 3
Frontier Logo
5:05 pm - 9:06 amISP-STL
17h 01m2 stops
Frontier Logo
7:55 pm - 10:55 amSTL-ISP
14h 00m2 stops
$280Frontier
Find Deal
Fri, Sep 12 - Fri, Sep 19
Southwest Logo
5:30 am - 1:30 pmISP-STL
9h 00m1 stop
Southwest Logo
7:15 am - 2:55 pmSTL-ISP
6h 40m1 stop
$288Southwest
Find Deal
Wed, Sep 17 - Sat, Sep 20
Southwest Logo
5:30 am - 1:30 pmISP-STL
9h 00m1 stop
Southwest Logo
11:50 am - 9:40 pmSTL-ISP
8h 50m2 stops
$293Southwest
Find Deal
Wed, Sep 17 - Sat, Sep 20
Southwest Logo
6:05 am - 1:30 pmISP-STL
8h 25m2 stops
Southwest Logo
11:50 am - 9:40 pmSTL-ISP
8h 50m2 stops
$311Southwest
Find Deal
Wed, Sep 17 - Sat, Sep 20

Frontier flights from Islip to St. Louis

Our best Frontier deals on Islip to St. Louis flight tickets
Frontier
Sep 26
ISP5:05 pmIslip Long Island
41h 49m
2 stops
STL9:54 amLambert-St Louis
Oct 3
STL9:32 pmLambert-St Louis
12h 23m
1 stop
ISP10:55 amIslip Long Island
$201
Find similar
Frontier
Sep 25
ISP11:40 amIslip Long Island
26h 22m
1 stop
STL1:02 pmLambert-St Louis
Sep 28
STL1:52 pmLambert-St Louis
19h 48m
1 stop
ISP10:40 amIslip Long Island
$234
Find similar
Frontier
Sep 26
ISP5:05 pmIslip Long Island
17h 01m
2 stops
STL9:06 amLambert-St Louis
Sep 29
STL4:00 pmLambert-St Louis
17h 40m
2 stops
ISP10:40 amIslip Long Island
$235
Find similar

Southwest flights from Islip to St. Louis

Our best Southwest deals on Islip to St. Louis flight tickets
Southwest
Sep 17
ISP5:30 amIslip Long Island
9h 00m
1 stop
STL1:30 pmLambert-St Louis
Sep 20
STL7:15 amLambert-St Louis
6h 40m
1 stop
ISP2:55 pmIslip Long Island
$288
Find similar
Southwest
Sep 17
ISP5:30 amIslip Long Island
9h 00m
1 stop
STL1:30 pmLambert-St Louis
Sep 20
STL11:50 amLambert-St Louis
8h 50m
2 stops
ISP9:40 pmIslip Long Island
$293
Find similar
Southwest
Sep 17
ISP6:05 amIslip Long Island
8h 25m
2 stops
STL1:30 pmLambert-St Louis
Sep 20
STL11:50 amLambert-St Louis
8h 50m
2 stops
ISP9:40 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 September 1, 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

Fri 9/26

5:05 pm-9:54 am

2 stops41h 49m

Lambert-St Louis

Fri 10/3

9:32 pm-10:55 am

1 stop12h 23m

$201

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 9/25

11:40 am-1:02 pm

1 stop26h 22m

Lambert-St Louis

Sun 9/28

1:52 pm-10:40 am

1 stop19h 48m

$234

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 9/26

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Mon 9/29

4:00 pm-10:40 am

2 stops17h 40m

$235

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 9/26

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Sun 9/28

10:39 am-10:40 am

2 stops23h 01m

$238

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Thu 9/25

11:40 am-1:02 pm

1 stop26h 22m

Lambert-St Louis

Sun 9/28

10:39 am-10:40 am

2 stops23h 01m

$243

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 9/26

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Fri 10/3

7:55 pm-10:55 am

2 stops14h 00m

$246

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Fri 9/12

5:05 pm-9:06 am

2 stops17h 01m

Lambert-St Louis

Fri 9/19

7:55 pm-10:55 am

2 stops14h 00m

$280

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 9/17

5:30 am-1:30 pm

1 stop9h 00m

Lambert-St Louis

Sat 9/20

7:15 am-2:55 pm

1 stop6h 40m

$288

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 9/17

5:30 am-1:30 pm

1 stop9h 00m

Lambert-St Louis

Sat 9/20

11:50 am-9:40 pm

2 stops8h 50m

$293

IslipSt. Louis

ISP - STL

ISPSTL

Islip Long Island

Wed 9/17

6:05 am-1:30 pm

2 stops8h 25m

Lambert-St Louis

Sat 9/20

11:50 am-9:40 pm

2 stops8h 50m

$311

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 20 resultsSorted by cheapest first
1
2

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 $332. 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 $439. 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 $392 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 8h 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
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.

An easier way to manage your St. Louis trip

We make it super easy to schedule, organize and travel with friends or family. Trips is free — and available to use no matter where you book.
Start using Trips
Find my bookings

Get notified when prices go down

Daily price changes in your inbox - only with Price Alerts.
1 adult
Sat 9/6
Sat 9/13
By creating a price alert you accept our terms of use and privacy policy.

Find better results for your trip to the United States